John O'Riley-O'Sullivan (born 29 January 2006) is an Irish professional footballer who plays as a midfielder for League of Ireland Premier Division club Drogheda United, on loan from Shamrock Rovers.
Ringsend man O'Sullivan began playing schoolboy football with local club Cambridge Boys, before moving to Cherry Orchard and then in 2019 he joined the academy of League of Ireland club Shamrock Rovers, playing for their under-13 side in his first year, then moving up to their under-15s in 2021 and training with the first team during pre-season of 2022, before playing for the club's under-17 and under-20 teams.
On 13 March 2023, O'Sullivan made his senior debut for Shamrock Rovers in a 2âÂÂ1 loss away to Bray Wanderers in a Leinster Senior Cup tie at the Carlisle Grounds. He made his league debut for the club on 29 April 2024, replacing Daniel Cleary from the bench in a 4âÂÂ0 win over Drogheda United at Tallaght Stadium.
On 28 July 2024, he was loaned out to League of Ireland First Division club Bray Wanderers until the end of the season. He made his debut for the club 2 August 2024, opening the scoring in a 2âÂÂ1 win away to Finn Harps. On 2 November 2024, O'Sullivan scored the winning penalty in a shootout win over Athlone Town at Dalymount Park to earn his side a place in the 2024 League of Ireland Promotion/Relegation Final against Drogheda United.
O'Sullivan returned to Rovers after his loan spell and on 20 February 2025, O'Sullivan made his European debut, coming off the bench in extra time against Molde of Norway and scoring his penalty in the shootout as his side were defeated and knocked out of the UEFA Conference League at the Knockout Phase Playoff stage.
On 14 July 2025, O'Sullivan signed for fellow League of Ireland Premier Division side Drogheda United on loan until the end of the season. On 18 July 2025, he scored on hide debut for the club, in a 5âÂÂ0 win at home to Crumlin United in the first game of his side's FAI Cup defence. He made a total of 6 appearances in all competitions during his loan spell spell, scoring once.
O'Sullivan played his first game since his loan when he came off the bench in a 2âÂÂ0 win away to Sligo Rovers. The following week, he assisted Aaron Greene with a through ball in a 2âÂÂ0 win over Galway United at Tallaght Stadium.
O'Sullivan has represented the Republic of Ireland at various underage levels. On 5 September 2024, he made his debut for the Republic of Ireland U19 team in a 2âÂÂ1 loss to France U19 in Slovenia.