Summerville-Princeton-Southern Bay is a local service district and designated place in the Canadian province of Newfoundland and Labrador.
Summerville-Princeton-Southern Bay is in Newfoundland within Subdivision F of Division No. 7. It consists of the communities of Summerville, Princeton and Southern Bay.
As a designated place in the 2016 Census of Population conducted by Statistics Canada, Summerville-Princeton-Southern Bay recorded a population of 310 living in 153 of its 229 total private dwellings, a change of from its 2011 population of 367. With a land area of , it had a population density of in 2016.
Summerville-Princeton-Southern Bay is a local service district (LSD) that is governed by a committee responsible for the provision of certain services to the community. The chair of the LSD committee is Tony Harris.