Michigan–Ontario League was the name of an American professional baseball league. It operated seven full seasons and part of an eighth from 1919 to 1926.

In 1926, the Michigan–Ontario League merged with the Central League to form the Michigan State League, which played only the one season.

• Battle Creek, MI: Battle Creek Custers 1919–1920
• Bay City, MI: Bay City Wolves 1919–1926
• Brantford, ON: Brantford Red Sox 1919–1921; Brantford Brants 1922
• Flint, MI: Flint Halligans 1919–1920; Flint Vehicles 1921–1926
• Grand Rapids, MI: Grand Rapids Billbobs 1923; Grand Rapids Homoners 1924
• Hamilton, ON: Hamilton Tigers 1919–1923; Hamilton Clippers 1924–1925
• Kalamazoo, MI: Kalamazoo Celery Pickers 1923; Kalamazoo Kazoos 1924
• Kitchener, ON: Kitchener Beavers 1919–1921; Kitchener Terriers 1922; Kitchener Colts 1925
• London, ON: London Tecumsehs 1919–1924; London Indians 1925
• Muskegon, MI: Muskegon Anglers 1923–1924
• Port Huron, MI: Port Huron Saints 1921; Port Huron Saints 1926
• Port Huron, MI & Sarnia, ON: Port Huron-Sarnia Saints 1922
• Saginaw, MI: Saginaw Aces 1919–1926