Maryland Route 450 (MD 450) is a state highway in the U.S. state of Maryland. The state highway runs 30.19 miles (48.59 km) from U.S. Route 1 Alternate (US 1 Alternate) in Bladensburg east to US 50, US 301, and MD 2 near Arnold. MD 450 forms a local complement to US 50 from near Washington, D.C. through Annapolis. In Prince George's County, the highway is a four- to six-lane divided highway that serves Bladensburg, Landover Hills, New Carrollton, Lanham, and Bowie. In Anne Arundel County, MD 450 connects Crofton with Parole and Annapolis with the portion of the county east of the Severn River. The highway serves as one of the main streets of Annapolis, including the state capital's historic core, and is the primary vehicular access to the U.S. Naval Academy.

MD 450 is the old alignment of US 50 from Bladensburg to Parole and of MD 2 from Parole to the Severn River. The MD 2 portion of the highway was constructed in the early to mid-1910s except for the first modern bridge across the Severn River, which was completed in the mid-1920s. The US 50 section of the highway was started from either end in the late 1910s and completed in the mid-1920s, shortly before the US 50 and MD 2 designations were assigned to the respective highways. As they were part of the main highways between Washington and Annapolis and from Annapolis to Baltimore, all segments of what is now MD 450 were improved in the 1920s and 1930s. The highway from the Severn River to Arnold was constructed as a relocated MD 2 in the late 1930s. MD 450 was first assigned from Crofton to Arnold in 1954 after US 50 was moved to its present freeway from Bowie to Arnold. The state highway was extended west to Bladensburg in 1962 when the US 50 freeway was completed from Bowie to Washington. MD 450 was expanded to a divided highway from Bladensburg to Lanham in the mid-1960s and from Lanham to Bowie in the early to mid-2000s.