San Marcos is an island located in the northern portion of Baja California Sur, México.

It faces the town of Santa Rosalía on the Gulf of California near Isla Tortuga.

A 1,125 meter long private-use dirt airstrip is located on the South coast of Isla San Marcos.

Small boats located in San Bruno ferry people to the island, and back from the island Fishing is the main attraction, being roughly in the middle of the Gulf of California.

This article about a location in the Mexican state of Baja California Sur is a stub.