The two-striped garter snake (Thamnophis hammondii ) is a species of aquatic garter snake, which is endemic to western North America.
T. hammondii is a medium-sized snake, 18-30 inches in total length (including tail), with a head barely wider than the neck. Two common color variations occur in the wild, a striped variant and a checkered variant. The striped variant has a yellowish lateral stripe on each side, and a fairly uniform dorsal coloring. The checkered variant lacks the lateral stripes and has two rows of small dark spots on each side.