Union Bay is an unincorporated community located south of Hart Creek on the east coast of central Vancouver Island, British Columbia. This Comox Valley community on BC Highway 19A is by road about 93 kilometres (58 mi) north of Nanaimo, and 14 kilometres (9 mi) south of Courtenay.

The Comox Valley is a region on the east coast of Vancouver Island, British Columbia, Canada, that includes the city of Courtenay, the town of Comox, the village of Cumberland, and the unincorporated settlements of Royston, Union Bay, Fanny Bay, Black Creek, and Merville. The communities of Denman Island and Hornby Island are also considered part of the Comox Valley. The Comox Valley contains the 47th largest metropolitan area in Canada with a population of about 76,000 as of 2022.