The narrow-headed garter snake, Thamnophis rufipunctatus, is a species of garter snake, endemic to the southwestern United States and adjacent northwestern Mexico. Its common names also include narrowhead garter snake and narrowhead watersnake.
The snake is blue-grey to olive-grey, or greenish to brown, and it has brown, orange, or black spots on the back. The total length of adults is 81–112 cm (32–44 in) (about 81–112 cm). It has eight or 9 upper labial scaless, one of which enters the eye, two or three preocular scales, two to four postoculars, and one anterior temporal scale. The keeled dorsal scales are arranged in 21 rows at midbody. Ventrals number 152–177; the anal plate is entire; the subcaudals number 65–87, and are divided.
It is found in Arizona and New Mexico, and in the Mexican states of Sonora, Chihuahua and Durango.
It is found near river banks or streams. It is one of the most aquatic of all garter snakes.
These snakes are piscivorous, meaning they primarily eat fish. Their diet includes dace, chubs, and both native and introduced trout. They might occasionally prey on salamanders.