San Marcos
- County:
- Hays County
- County Seat:
- Yes
- Area (mi²):
- 40.421
- State:
- Texas
San Marcos is a city located in Hays County, Texas. San Marcos has a 2026 population of 74,316. It is also the county seat of Hays County. San Marcos is currently growing at a rate of 3.31% annually and its population has increased by 8.93% since the most recent census, which recorded a population of 68,224 in 2020.