X0609 4 2026-09-04 0 0001288847 Five9, Inc. FIVN 0001886762 Meriweather Tiffany N. false C/O FIVE9, INC. 3001 BISHOP DRIVE, SUITE 350 SAN RAMON CA 94583 0 1 0 0 Chief Admin. & Legal Officer 1 Common Stock 2026-09-04 4 S 0 5600 33.02 D 266172 D Common Stock 2026-09-04 4 S 0 7809 33.51 D 258363 D Common Stock 2026-09-08 4 S 0 5114 31.55 D 253249 D The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on May 21, 2026. The reported sales were to cover taxes upon the vesting of restricted stock units. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $32.35 to $33.35, inclusive. The reporting person undertakes to provide Five9, Inc., any security holder of Five9, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $33.36 to $33.77, inclusive. The reporting person undertakes to provide Five9, Inc., any security holder of Five9, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $31.12 to $31.97, inclusive. The reporting person undertakes to provide Five9, Inc., any security holder of Five9, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. /s/ Leena Mansharamani, Attorney in Fact 2026-09-09