Thomas Paul O'Sullivan (born 18 January 1995) is a Welsh professional footballer who plays as a midfielder for National League North club Brackley Town.

A Wales youth international, he began his professional career with Cardiff City in 2012, making his debut in the League Cup in August 2012.

Born in Mountain Ash, Rhondda Cynon Taf,[4] O'Sullivan progressed through the Academy at Cardiff City to sign his first professional contract in 2012.

[5] He made his professional debut when he came on as a substitute for Stephen McPhail 19 minutes into a 2–1 League Cup defeat to Northampton Town at Sixfields Stadium on 14 August 2012.

[9] Ten days later he was re-signed by Page on another one-month loan, after the departure of Chris Lines created a midfield vacancy in Vale's first-team picture.

[16] In total he made 13 appearances for the club during the loan spell, which was not extended despite Cardiff manager Russell Slade being encouraged by O'Sullivan's progress.

[21] He made his debut as a substitute for Drey Wright after 78-minutes of Colchester's 4–0 League Two win at home to Stevenage on 8 April.

[25] He played a total of seven games for Gary Owers's "Gulls", who ended the season being relegated into the National League South.

[27] On 25 October 2018, O'Sullivan signed with National League North side Hereford after a successful trial period at Edgar Street.

[30] On 7 August 2020, O'Sullivan joined Hereford's National League North rivals Gloucester City, becoming manager James Rowe's fifth summer signing.