Gary O'Sullivan has six losses against six opponents on his boxing record. For a list of O'Sullivan's best fights, refer to "Best fights of Gary O'Sullivan".
On March 17, 2024 Gary O'Sullivan faced off against Sofiane Khati in a middleweight bout at age 39. He was coming in with a record of 31-6 (21). O'Sullivan lost the fight via 8-round points decision.
On May 28, 2022 Gary O'Sullivan fought Erislandy Lara in a middleweight world-title fight for Lara's WBA (Regular) title. O'Sullivan was 37 years old and with a record of 31-5 (21), and Lara was 39 years old and with a record of 28-3-3 (16). O'Sullivan lost the fight via 8th-round TKO.
On January 11, 2020 Gary O'Sullivan faced off against Jaime Munguia at age 35. He was coming in with a record of 30-4 (21), and Munguia was 23 years old and with a record of 34-0 (27). O'Sullivan lost the fight via 11th-round TKO.
On September 15, 2018 Gary O'Sullivan faced off against David Lemieux at age 34. He was coming in with a record of 28-3 (20), and Lemieux was 29 years old and with a record of 39-4 (33). O'Sullivan lost the fight via 1st-round KO.
On December 12, 2015 Gary O'Sullivan faced off against Chris Eubank Jr. at age 31. He was coming in with a record of 22-2 (15), and Eubank Jr. was 26 years old and with a record of 20-1 (15). O'Sullivan lost the fight via 7th-round retirement.
On July 20, 2013 Gary O'Sullivan faced off against Billy Joe Saunders in a middleweight bout at age 29. He was coming in with a record of 16-1 (10), and Saunders was 23 years old and with a record of 17-0 (10). O'Sullivan lost the fight via 12-round unanimous decision.
