From Spanish "Saint Mark", also known as Mark the Evangelist.
- A village and rural municipality of Salta Province, Argentina.
- A town in Antioquia department, Colombia.
- A town in Sucre department, Colombia.
- The capital city of Tarrazú canton, San José, Costa Rica, also known as San Marcos de Tarrazú.
- An urban parish of Quito, Ecuador.
- A municipality and suburb of San Salvador, El Salvador.
- A city and municipality, the capital of San Marcos department, Guatemala.
- A municipality of Ocotepeque department, Honduras.
- A municipality of Santa Bárbara department, Honduras.
- An island in Baja California Sur, Mexico.
- A town, a municipal seat in San Marcos, Guerrero, Mexico.
- A town and municipality of Jalisco, Mexico.
- A municipality of Carazo department, Nicaragua.
- A town, the capital of San Marcos, Cajamarca department, Peru.
- A city in San Diego County, California, United States: San Marcos, California.
- A city, the county seat of Hays County, Texas, United States: San Marcos, Texas.
- A river in Texas, United States: the San Marcos River.