Cassin is an unincorporated community in Bexar County, in the U.S. state of Texas.

It is located within the Greater San Antonio metropolitan area.

The community served as a flag stop station for the San Antonio, Uvalde and Gulf Railroad in 1913.

[2] Cassin is located off U.S. Highway 281, just south of Mitchell Lake, 12 mi (19 km) south of Downtown San Antonio in southern Bexar County.

[2] Today, the community is served by the Southside Independent School District.