Exhibit 24(a)

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 27th day of October, 2008.

/s/  Alain J.P. Belda

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Win Bischoff

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Kenneth T. Derr

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  John M. Deutch

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 23rd day of October, 2008.

/s/  Roberto Hernández Ramirez

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Andrew N. Liveris

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Anne M. Mulcahy

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Richard D. Parsons

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Lawrence R. Ricciardi

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Judith Rodin

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Robert E. Rubin

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Robert L. Ryan

POWER OF ATTORNEY

(Form S-3)

KNOW ALL MEN BY THESE PRESENTS, that the undersigned, a director of CITIGROUP INC., a Delaware corporation (the “Company”), does hereby constitute and appoint Vikram Pandit, Gary Crittenden and Michael S. Helfer, and each of them, the true and lawful attorneys-in-fact and agents of the undersigned, to do or cause to be done any and all acts and things and to execute any and all instruments and documents which said attorneys-in-fact and agents, or any of them, may deem advisable or necessary to enable the Company to comply with the Securities Act of 1933, as amended, and any rules, regulations and requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration of the securities of the Company, or the securities guaranteed by the Company, being registered on the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit (the “Securities”), including specifically, but without limiting the generality of the foregoing, power and authority to sign, in the name and on behalf of the undersigned as a director of the Company, the Registration Statement on Form S-3 to which this power of attorney is filed as an exhibit, or another appropriate form in respect of the registration of the Securities, and any and all amendments thereto, including post-effective amendments, and any instruments, contracts, documents or other writings of which the originals or copies thereof are to be filed as a part of, or in connection with, the Registration Statement, any other appropriate form or any amendments thereto, and to file or cause to be filed the same with the Securities and Exchange Commission, and to effect any and all applications and other instruments in the name and on behalf of the undersigned which said attorneys-in-fact and agents, or any of them, deem advisable in order to qualify or register the Securities under the securities laws of any of the several States; and the undersigned does hereby ratify all that said attorneys-in-fact or agents, or any of them, shall do or cause to be done by virtue thereof.

IN WITNESS WHEREOF, the undersigned has signed these presents this 21st day of October, 2008.

/s/  Franklin A. Thomas