144 0002063775 XXXXXXXX LIVE 0001288847 Five9, Inc. 001-36383 3001 BISHOP DR. SUITE #350 San Ramon CA 94583 925-201-2000 Bryan Lee Officer Common Morgan Stanley Smith Barney LLC Executive Financial Services 1 New York Plaza 8th Floor New York NY 10004 4769 119358.17 74723569 06/04/2026 Nasdaq Common 06/03/2026 RSU Issuer N 4769 06/03/2026 Not Applicable N Bryan Lee 3001 Bishop Drive Suite 350 San Ramon CA 94583 Common 03/04/2026 9855 174433.5 Bryan Lee 3001 Bishop Drive Suite 350 San Ramon CA 94583 Common 03/05/2026 1756 31467.52 The sale reported on this Form 144 represents an Issuer mandated sale by the Reporting Person to cover tax withholding obligations in connection with the vesting and settlement of Restricted Stock Units, and it does not represent a discretionary trade by the Reporting Person. 06/03/2026 Bryan Lee