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 Annapolis. MD 450 is the original alignment of US 50 in Prince George's and Anne Arundel Counties. The state highway was assigned to sections of old US 50 in the 1950s as US 50 was gradually moved to the limited-access John Hanson Highway.

MD 450 begins at an intersection with US 1 Alternate in Bladensburg. The state highway heads east as Annapolis Road through Bladensburg, passing through an interchange with MD 201, a wye intersection with MD 202, and an interchange with the Baltimore-Washington Parkway. MD 450 heads into Landover Hills, where the highway meets MD 410 and its interchange with the Capital Beltway, then crosses the Amtrak Northeast Corridor immediately after a partial interchange with MD 564. The state highway continues east through Lanham, where the road intersects MD 704 and MD 193. After crossing CSX's Popes Creek Subdivision, MD 450 crosses MD 197 in Bowie. The state highway joins MD 3 in a concurrency on the east side of Bowie; the two highways cross the Patuxent River together on the Priest Bridge into Anne Arundel County.

Shortly after the bridge, MD 450 separates from MD 3 and heads east as Defense Highway through Crofton, where the highway intersects MD 424. The state highway continues east through a hilly area where the highway passes under I-97. MD 450 continues east into Annapolis, where the highway meets MD 178 adjacent to the Annapolis Mall. After an interchange with US 50 and US 301, the state highway continues into Annapolis as West Street. MD 450 meets MD 2 on the west side of the city then intersects MD 435 and MD 387 at Westgate Circle. The state highway passes through Church Circle, from which the highway continues as College Avenue. After intersecting the southern terminus of MD 70, MD 450 turns north onto King George Street. The state highway follows the edge of the campus of the United States Naval Academy northwest and then northeast after the junction with the other end of MD 435. MD 450 crosses the Severn River on the Naval Academy Bridge and meets MD 648 on the other side. The state highway, now following Governor Ritchie Highway, turns to the northwest before reaching its eastern terminus at an interchange with US 50, US 301, and MD 2.

MD 450 is the old alignment of US 50 between Bladensburg and Annapolis. The portion east of downtown Annapolis was also once part of MD 2. MD 450 was assigned to the highway it follows as sections of John Hanson Highway were completed in the 1950s.