- A surname.
- a township in south-western Ontario, Canada.
- a city in St. Clair County, Michigan, USA.
- a small city in Blue Earth County, Minnesota, USA.
- a borough in Schuylkill County, Pennsylvania, USA.
- a neighbourhood in Pittsburgh, Pennsylvania.
Only places spelt St. Clair (and not St Clair or Saint Clair) are included; British practice usually differs from American and Canadian practice.