Montana Highway 16 is a 152.371-mile-long (245.217 km) state highway in the U.S. state of Montana. It begins in West Glendive at a Business Loop of Interstate 94 (I-94), and ends at the Port of Raymond on the Saskatchewan border. The northern portion from U.S. Route 2 at Culbertson to the Canada–United States border is proposed as part of the Theodore Roosevelt Expressway.

The Theodore Roosevelt Expressway, is made up of several existing highways between Rapid City, South Dakota and the Port of Raymond between Saskatchewan and Montana. It is the northern third of the Ports-to-Plains Alliance. The corridor is approximately 445 miles (716 km) long with the majority of the highway two lanes. Congress designated the route as one of 80 National Highway System High-Priority Corridors in 2005 by the Intermodal Surface Transportation Efficiency Act. The designation did not create new design standards or create new eligibility for any additional federal funding.