The bullsnake (Pituophis catenifer sayi) is a large non-venomous colubrid snake, widespread in the central part of the United States, northern Mexico, and southwestern Saskatchewan and Alberta Canada. It is currently considered a subspecies of the gopher snake (Pituophis catenifer). The epithet sayi is in honor of zoologist Thomas Say.
Bullsnakes average about 6 feet (1.8 m) in length, and specimens of up to 8 feet 4 inches (2.5 m) have been recorded. Adult specimens have been weighed from 1–3.6 kg (2.2–7.9 lb), though the heaviest known specimens can attain 4.5 kg (9.9 lb). This makes the bullsnake among the largest snakes native to the United States, although it is generally not as long as indigo snakes nor as heavy or as large in diameter as rattlesnakes. They are usually yellow in color, with brown, black or sometimes reddish colored blotching. The blotching pattern is as follows: large blotches on top, three sets of spots on the sides, and bands of black on the tail. Many color variations have been found, including albinos and white varieties. A scale count is required to distinguish juvenile bullsnakes from juvenile gopher snakes.