Highway 55 (MT 55) in the U.S. State of Montana is a route running in a northerly direction from an intersection with MT 41 about 4 miles (6.4 km) north of the small town of Silver Star.

The highway extends approximately 13 miles (21 km) to an interchange with Interstate 90 (I-90) at the north edge of the town of Whitehall.

The route traverses largely agricultural land in the Jefferson River valley.

Highway 55 begins at MT 41, north of Silver Star.

A small segment of Highway 55 in Whitehall was a former alignment of U.S. Route 10, before U.S. 10 was deleted across Montana.