Thamnophis eques (Reuss 1834)

Continent: Middle-America North-America
Distribution: USA (S Arizona, New Mexico), Mexico (from the vicinity of the Pico de Orizaba northwestward to and south to Aguascalientes, Sonora and Chihuahua. Rossman et al. [1996: 173] mapped the range and showed disjunct colonies in Oaxaca and Nuevo León). carmenensis: Tlaxcala (La Lagunilla del Carmen);
Type locality: near El Carmen, Tlaxcala, Mexico. cuitzeoensis: Michoacán;
Type locality: 100 m east of the southern end of the south“north causeway across the Lago de Cuitzeo, Michoacán, Mexico. diluvialis: Jalisco, Cajititlán and several isolated localities;
Type locality: near Villa Corona at the north end of the Laguna de Atotonilco, Jalisco, Mexico. insperatus: Michoacán;
Type locality: on the highway 6 km southeast of Zacapu, Michoacán, Mexico. obscurus: Jalisco;
Type locality: town of Chapala, Jalisco, Mexico. patzcuaroensis: Michoacán;
Type locality: lakeshore north of the town of Pátzcuaro, Michoacán, Mexico. scotti: Jalisco;
Type locality: near Magdalena, Lago de Magdalena, Jalisco, Mexico. virgatenuis: highlands of Durango and Chihuahua

The Mexican garter snake (Thamnophis eques) is a species of snake of the family Colubridae. It is found in Mexico and in the United States (Arizona and New Mexico). This essentially harmless snake is semi-aquatic and most of the 10 recognized subspecies are restricted to lake basins in Mexico.