UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 3)*

TUNIU CORPORATION

(Name of Issuer)

Class A Ordinary Shares, $0.0001 par value per share

(Title of Class of Securities)

89977P106

(CUSIP Number)

Sequoia Capital 2010 CV Holdco, Ltd.

3613, 36/F

Two Pacific Place

88 Queensway

Hong Kong, PRC

Attention: Neil Nanpeng Shen

Telephone: (852) 2501 8989

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

with copies to:

Craig Marcus

Ropes & Gray LLP

800 Boylston Street

Boston, Massachusetts 02199

(617) 951-7802

May 22, 2015

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ¨

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 89977P106 SCHEDULE 13D Page 2 of 12

1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) Sequoia Capital 2010 CV Holdco, Ltd. IRS Identification No. 98-0660286
2.	Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  ¨
3.	SEC Use Only
4.	Source of Funds (See Instructions) OO
5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ¨
6.	Citizenship or Place of Organization Cayman Islands
Number of Shares Beneficially Owned by Each Reporting Person With		7.	Sole Voting Power 0
		8.	Shared Voting Power 19,531,697
		9.	Sole Dispositive Power 0
		10.	Shared Dispositive Power 19,531,697
11.	Aggregate Amount Beneficially Owned by Each Reporting Person 19,531,697
12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) ¨
13.	Percent of Class Represented by Amount in Row (11) 10.3%
14.	Type of Reporting Person (See Instructions) OO

CUSIP No. 89977P106 SCHEDULE 13D Page 3 of 12

1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) Sequoia Capital China Venture 2010 Fund, L.P. IRS Identification No. 98-0678098
2.	Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  ¨
3.	SEC Use Only
4.	Source of Funds (See Instructions) OO
5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ¨
6.	Citizenship or Place of Organization Cayman Islands
Number of Shares Beneficially Owned by Each Reporting Person With		7.	Sole Voting Power 0
		8.	Shared Voting Power 19,531,697
		9.	Sole Dispositive Power 0
		10.	Shared Dispositive Power 19,531,697
11.	Aggregate Amount Beneficially Owned by Each Reporting Person 19,531,697
12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) ¨
13.	Percent of Class Represented by Amount in Row (11) 10.3%
14.	Type of Reporting Person (See Instructions) PN

CUSIP No. 89977P106 SCHEDULE 13D Page 4 of 12

1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) SC China Venture 2010 Management, L.P. IRS Identification No. 98-0678096
2.	Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  ¨
3.	SEC Use Only
4.	Source of Funds (See Instructions) OO
5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ¨
6.	Citizenship or Place of Organization Cayman Islands
Number of Shares Beneficially Owned by Each Reporting Person With		7.	Sole Voting Power 0
		8.	Shared Voting Power 19,531,697
		9.	Sole Dispositive Power 0
		10.	Shared Dispositive Power 19,531,697
11.	Aggregate Amount Beneficially Owned by Each Reporting Person 19,531,697
12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) ¨
13.	Percent of Class Represented by Amount in Row (11) 10.3%
14.	Type of Reporting Person (See Instructions) PN

CUSIP No. 89977P106 SCHEDULE 13D Page 5 of 12

1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) SC China Holding Limited IRS Identification No. – N/A
2.	Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  ¨
3.	SEC Use Only
4.	Source of Funds (See Instructions) OO
5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ¨
6.	Citizenship or Place of Organization Cayman Islands
Number of Shares Beneficially Owned by Each Reporting Person With		7.	Sole Voting Power 0
		8.	Shared Voting Power 19,531,697
		9.	Sole Dispositive Power 0
		10.	Shared Dispositive Power 19,531,697
11.	Aggregate Amount Beneficially Owned by Each Reporting Person 19,531,697
12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) ¨
13.	Percent of Class Represented by Amount in Row (11) 10.3%
14.	Type of Reporting Person (See Instructions) OO

CUSIP No. 89977P106 SCHEDULE 13D Page 6 of 12

1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) SNP China Enterprises Limited IRS Identification No. – N/A
2.	Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  ¨
3.	SEC Use Only
4.	Source of Funds (See Instructions) OO
5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ¨
6.	Citizenship or Place of Organization British Virgin Islands
Number of Shares Beneficially Owned by Each Reporting Person With		7.	Sole Voting Power 0
		8.	Shared Voting Power 19,531,697
		9.	Sole Dispositive Power 0
		10.	Shared Dispositive Power 19,531,697
11.	Aggregate Amount Beneficially Owned by Each Reporting Person 19,531,697
12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) ¨
13.	Percent of Class Represented by Amount in Row (11) 10.3%
14.	Type of Reporting Person (See Instructions) OO

CUSIP No. 89977P106 SCHEDULE 13D Page 7 of 12

1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) Neil Nanpeng Shen
2.	Check the Appropriate Box if a Member of a Group (See Instructions) (a)  ¨        (b)  ¨
3.	SEC Use Only
4.	Source of Funds (See Instructions) OO
5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ¨
6.	Citizenship or Place of Organization Hong Kong SAR
Number of Shares Beneficially Owned by Each Reporting Person With		7.	Sole Voting Power 0
		8.	Shared Voting Power 19,531,697
		9.	Sole Dispositive Power 0
		10.	Shared Dispositive Power 19,531,697
11.	Aggregate Amount Beneficially Owned by Each Reporting Person 19,531,697
12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) ¨
13.	Percent of Class Represented by Amount in Row (11) 10.3%
14.	Type of Reporting Person (See Instructions) IN

Except as set forth in this Amendment No. 3 (this “Amendment”), the Schedule 13D as initially filed on May 19, 2014, amended by Amendment No. 1 thereto on January 12, 2015 and Amendment No. 2 thereto on May 18, 2015, remains in effect, and capitalized terms used herein but not defined herein have such respective meanings, as defined in such Schedule 13D. The information set forth in response to each separate Item below shall be deemed to be a response to all Items where such information is relevant. The information set forth in the Exhibits attached hereto and to the initial Schedule 13D filing is expressly incorporated herein by reference and the response to each Item of this Statement is qualified in its entirety by the provisions of such Exhibits.

ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

Item 3 is hereby amended and supplemented by adding the following new paragraph:

On May 22, 2015, SC CV HOLD purchased 1,875,000 newly issued Class A Shares from the Company pursuant to the previously disclosed Subscription Agreement at an aggregate purchase price of $10,000,000, or approximately $5.33 per Class A Share, which represents the equivalent of the approximate average closing trading price of the Company’s ADSs for the 20 trading days prior to the signing of Subscription Agreement. Pursuant to the previously disclosed definitive agreements between the Company and a group of investors, on May 22, 2015 the Company issued and sold to such group of investors approximately $480,000,000 in newly issued Class A Shares, including the Class A Shares purchased by SC CV HOLD pursuant to the Subscription Agreement. Upon consummation of the closing, the Reporting Persons beneficially own approximately 10.3% of the Company’s outstanding Class A Shares, representing a decrease in the percentage of beneficial ownership as a result of dilution.

ITEM 4. PURPOSE OF TRANSACTION.

Item 4 is hereby amended and supplemented by adding the following paragraphs:

As described in Item 3 above, which descriptions are incorporated by reference in this Item 4, this Amendment is being filed in connection with the Reporting Persons’ acquisition of 1,875,000 of the Company’s newly issued Class A Shares. Such Class A Shares were acquired by the Reporting Persons for investment purposes.

Except as set forth in this Item 4, the Reporting Persons have no present plans or proposals that relate to or would result in any of the actions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. The Reporting Persons do, however, reserve the right in the future to adopt such plans or proposals subject to compliance with applicable regulatory requirements.

ITEM 5. INTEREST IN SECURITIES OF THE ISSUER.

Paragraphs (a), (b) and (c) of Item 5 are hereby amended and restated in their entirety as follows:

(a) The aggregate number of Class A Shares and the percentage of total outstanding Class A Shares beneficially owned by the Reporting Persons is set forth below. References to percentage ownerships of Class A Shares in this Statement are based upon the 175,526,210 Class A Shares outstanding as of May 22, 2015 as told to the Reporting Persons by the Company. The Reporting Persons may be deemed to beneficially own an aggregate of 19,531,697 Class A Shares (consisting entirely of (i) 14,323,364 Class A Shares that can be acquired upon the conversion of outstanding Class B Shares, (ii) 1,875,000 Class A Shares directly held, and (iii) 3,333,333 Class A Shares in the form of 1,111,111 ADSs), which constitutes approximately 10.3% of the Company’s Class A Shares, calculated in accordance with Rule 13d-3 under the Act. The filing of this Statement shall not be construed as an admission that a Reporting Person beneficially owns those shares held by any other Reporting Person.

SC CV HOLD beneficially owns 19,531,697 Class A Shares (consisting entirely of (i) 14,323,364 Class A Shares that can be acquired upon the conversion of outstanding Class B Shares, (ii) 1,875,000 Class A Shares directly held, and (iii) 3,333,333 Class A Shares in the form of 1,111,111 ADSs), which represents approximately 10.3% of the outstanding Class A Shares calculated in accordance with the requirements of Rule 13d-3 under the Act.

SCC Venture, as the parent company of SC CV HOLD, may be deemed to beneficially own 19,531,697 Class A Shares (consisting entirely of (i) 14,323,364 Class A Shares that can be acquired upon the conversion of outstanding Class B Shares, (ii) 1,875,000 Class A Shares directly held, and (iii) 3,333,333 Class A Shares in the form of 1,111,111 ADSs), which represents approximately 10.3% of the outstanding Class A Shares calculated in accordance with the requirements of Rule 13d-3 under the Act.

SCC MGMT, as the general partner of SCC Venture, may be deemed to beneficially own an aggregate of 19,531,697 Class A Shares (consisting entirely of (i) 14,323,364 Class A Shares that can be acquired upon the conversion of outstanding Class B Shares, (ii) 1,875,000 Class A Shares directly held, and (iii) 3,333,333 Class A Shares in the form of 1,111,111 ADSs), which represents approximately 10.3% of the outstanding Class A Shares calculated in accordance with the requirements of Rule 13d-3 under the Act.

SCC HOLD, as the general partner of SCC MGMT, may be deemed to beneficially own an aggregate of 19,531,697 Class A Shares (consisting entirely of (i) 14,323,364 Class A Shares that can be acquired upon the conversion of outstanding Class B Shares, (ii) 1,875,000 Class A Shares directly held, and (iii) 3,333,333 Class A Shares in the form of 1,111,111 ADSs), which represents approximately 10.3% of the outstanding Class A Shares calculated in accordance with the requirements of Rule 13d-3 under the Act.

SNP, which is the parent company of SCC HOLD, may be deemed to beneficially own an aggregate of 19,531,697 Class A Shares (consisting entirely of (i) 14,323,364 Class A Shares that can be acquired upon the conversion of outstanding Class B Shares, (ii) 1,875,000 Class A Shares directly held, and (iii) 3,333,333 Class A Shares in the form of 1,111,111 ADSs), which represents approximately 10.3% of the outstanding Class A Shares calculated in accordance with the requirements of Rule 13d-3 under the Act.

Neil Nanpeng Shen, who wholly owns and is the sole director of SNP, may be deemed to beneficially own an aggregate of 19,531,697 Class A Shares (consisting entirely of (i) 14,323,364 Class A Shares that can be acquired upon the conversion of outstanding Class B Shares, (ii) 1,875,000 Class A Shares directly held, and (iii) 3,333,333 Class A Shares in the form of 1,111,111 ADSs), which represents approximately 10.3% of the outstanding Class A Shares calculated in accordance with the requirements of Rule 13d-3 under the Act.

By virtue of the relationship described herein, the Reporting Persons may be deemed to constitute a “group” for purposes of Rule 13(d)(3) of the Act. The filing of this Statement shall not be construed as an admission that a Reporting Person beneficially owns those shares held by any other member of the group. In addition, each Reporting Person expressly disclaims beneficial ownership of any securities reported herein except to the extent such Reporting Person actually exercises voting or dispositive power with respect to such securities.

(b) The number of Class A Shares as to which each of the Reporting Persons has sole or shared power to vote, direct the vote, dispose or direct the disposition are as set forth in rows seven through ten of the cover pages hereof. The information set forth in Item 2 is hereby incorporated by reference into this Item 5(b).

(c) Except with respect to the acquisition of Class A Shares acquired pursuant to the Subscription Agreement, as more fully described in Items 3 and 4, and as set forth in this Item 5, the Reporting Persons have not effected any transactions in the Class A Shares during the past 60 days.

SIGNATURES

After reasonable inquiry and to the best of its knowledge and belief, the undersigned certifies that the information set forth in this Statement is true, complete and correct.

Dated: May 26, 2015

SEQUOIA CAPITAL 2010 CV HOLDCO, LTD.

/s/ Kok Wai Yee                                                     

Name: Kok Wai Yee

Title: Authorized Signatory

SEQUOIA CAPITAL CHINA VENTURE 2010

FUND, L.P.

By: SC China Venture 2010 Management, L.P.

A Cayman Islands exempted limited partnership,

Its General Partner

By: SC China Holding Limited

A Cayman Islands limited liability company

Its General Partner

/s/ Kok Wai Yee                                                     

Name: Kok Wai Yee

Title: Authorized Signatory

SC CHINA VENTURE 2010 MANAGEMENT, L.P.

By: SC China Holding Limited

A Cayman Islands limited liability company

Its General Partner

/s/ Kok Wai Yee                                                     

Name: Kok Wai Yee

Title: Authorized Signatory

SC CHINA HOLDING LIMITED

/s/ Kok Wai Yee                                                     

Name: Kok Wai Yee

Title: Authorized Signatory

SNP CHINA ENTERPRISES LIMITED

/s/ Neil Nanpeng Shen                                           

Name: Neil Nanpeng Shen

Title: Authorized Signatory

NEIL NANPENG SHEN

/s/ Neil Nanpeng Shen                                           

Name: Neil Nanpeng Shen