Osgar O'Hoisin (; born 3 September 1996) is an Irish tennis player. He has a career high ATP singles ranking of No. 732 achieved on 22 May 2023 and a career high doubles ranking of No. 587 achieved on 2 February 2024.
He attended the University of WisconsinâÂÂMadison, and played for the Wisconsin Badgers tennis team between 2015 and 2019.
O'Hoisin is a multiple time club champion in his boyhood club Donnybrook Tennis Club, in Dublin, Ireland. He was Irish under-18 champion in 2012 and 2015.
O'Hoisin has represented Ireland at the Davis Cup since 2018. He has a winâÂÂloss record of 2âÂÂ7 in singles and 3âÂÂ1 in doubles. In 2022 he won the deciding match in Ireland's 3âÂÂ2 win against Barbados in the World Group II competition.
In February 2024, he was a member of the Irish team which lost to Austria in the World Group I play-offs in Limerick, suffering a straight sets defeat against Sebastian Ofner in the second singles match.