Sean Daniel O'Malley[4] (born October 24, 1994) is an American professional mixed martial artist.

[5] O'Malley trains in Glendale, Arizona, at The MMA Lab led by head trainer John Crouch,[6] and is coached by his long-time friend, Tim Welch.

[8] After his win over Nuzzo, O'Malley earned a spot on Dana White's Contender Series 2 where he took on Alfred Khashakyan.

O'Malley beat Khashakyan with a stunning knockout in the first round and was awarded a UFC contract.

[9] O'Malley's promotional debut came against Terrion Ware on December 1, 2017, at The Ultimate Fighter 26 Finale.

[19] However, O'Malley announced his withdrawal from the bout on June 21, 2019, due to a failed test for ostarine.

[24] O'Malley faced former WEC Bantamweight Champion Eddie Wineland at UFC 250 on June 6, 2020.

[34] However, Smolka pulled out of the fight in late June citing injury,[35] and he was replaced by promotional newcomer Kris Moutinho.

[42] Early in the second round, O'Malley accidentally poked Munhoz in the eye, rendering him unable to continue.

[45] The result was seen as highly controversial, with many fans and fighters expressing their belief that Yan was the rightful winner.

[51] For his first title defense, O'Malley faced Marlon Vera in a rematch on March 9, 2024, at UFC 299.

[54] For his second title defense, O'Malley faced Merab Dvalishvili on September 14, 2024 in the main event at UFC 306.

[56] On September 16, O'Malley revealed on his podcast that he suffered from a torn labrum from before the fight and that he will undergo surgery.

[59] Chael Sonnen put out an open challenge on behalf of O'Malley for his promotion's event on December 20, 2020.

[61][62] Together with his friend and head coach, Tim Welch, O'Malley is a co-host of their own podcast, The Timbo Sugarshow.