Union Bay in British Columbia, Canada is a small community approximately 15 kilometres south of Courtenay, British Columbia, the largest city in the Comox Valley. Union Bay is populated by about 1200 people and is an unincorporated site within the Comox Valley Regional District.

The main drag along Highway 19A features a boatlaunch, sports/coffee shop, bistro and market/cafe. Also along the highway are the heritage Gaolhouse museum, Post Office, church, and now closed school that is currently used as the District Improvement Offices. 

Union Bay was first established as "Union Wharf" back in 1887. The community was developed as a port for the thriving coal mines at Union to the Northwest (later reincorporated as Cumberland).