Curling Ontario (formerly the Ontario Curling Association and CurlON) is the governing body of curling in Southern Ontario. Northern Ontario is governed by the Northern Ontario Curling Association (NOCA). The Curling Ontario sends a team to represent Team Ontario at all major Canadian Championships. The NOCA sends a separate team to all of these events.

Curling Ontario was founded in 1875 as the Ontario Curling Association. It was renamed CurlON in 2016 and as Curling Ontario in 2024.

The Ontario Tankard is the provincial championship for men's curling. The winner represents Team Ontario at The Brier.

Previous names:

The Ontario Women's Curling Championship, formerly the Ontario Scotties Tournament of Hearts is the provincial championship for women's teams. Unlike the Dominion Tankard, the women's championship included teams from both southern and northern Ontario until 2015. The winner of the provincial championship goes on to play in the national championship. Because the national champion returns the previous years champion to the event, if that team is from Ontario, they cannot defend their provincial championship. The national championship has been running since 1962, but the provincial championship has existed since 1956.

The U-21 provincial curling championships are held annually in early January. The tournament is for curlers 20 years old and younger. A men's tournament has been held since 1950 and the women's since 1972. The winning team represents Ontario at the Canadian Junior Curling Championships.

National champions in bold.

The Ontario Senior Championship is for curlers over 50. The winner represents Ontario at the Canadian Senior Curling Championships.