North Dakota Highway 91 (ND 91) is a 1.262-mile-long (2.031 km) north–south state highway in the U.S. state of North Dakota.

ND 91's southern terminus is at U.S. Route 81 (US 81) south of St. Thomas, and the northern terminus is at US 81 north of St.

Thomas.

[1] The entire route is in St. Thomas, Pembina County.