San Diego
- County:
- Duval County
- County Seat:
- Yes
- Area (mi²):
- 1.901
- State:
- Texas
San Diego is a city located in Duval County, Texas. San Diego has a 2026 population of 3,620. It is also the county seat of Duval County. San Diego is currently declining at a rate of -0.3% annually and its population has decreased by -3.36% since the most recent census, which recorded a population of 3,746 in 2020.