Maryland Route 704 (MD 704) is a state highway in the U.S. state of Maryland. Known as Martin Luther King Jr. Highway, the state highway runs 6.53 mi (10.51 km) from Eastern Avenue at the District of Columbia boundary in Seat Pleasant east to MD 450 in Lanham. MD 704 was constructed in the early 1940s from Seat Pleasant to U.S. Route 50 (now MD 450) along the right-of-way of the abandoned Washington, Baltimore and Annapolis Electric Railway. The highway was expanded to a multi-lane divided highway west of US 50 in the 1960s and 1970s and at its eastern end in 2000.

MD 704 begins at an intersection with Eastern Avenue near the eastern corner of the District of Columbia boundary. The highway continues south as 63rd Avenue, which heads south toward Southern Avenue and East Capitol Street. MD 704 heads northeast as a six-lane divided highway through the town of Seat Pleasant, where the highway intersects Addison Road. After leaving the town, the state highway crosses Cabin Branch and intersects Sheriff Road at an oblique angle. MD 704 passes through Palmer Park, where the highway traverses Cattail Branch and meets MD 202 (Landover Road) at a full cloverleaf interchange. MD 704 temporarily drops to four lanes through the MD 202 interchange.

MD 704 continues through Glenarden, where the highway intersects Ardwick Ardmore Road and crosses the Capital Beltway (Interstate 95 and I-495) with no access. MD 704 drops to four lanes again between Ardwick Ardmore Road and the five-ramp interchange at unsigned I-595 and US 50, which features a direct ramp to northbound I-95 and I-495 toward Baltimore. MD 704 continues northeast as a six-lane highway across Bald Hill Branch, through office parks, and past a shopping center before reaching its eastern terminus at MD 450 (Annapolis Road) in Lanham.

MD 704 was constructed in 1942 on the right-of-way of the Washington, Baltimore and Annapolis Electric Railway, which had ceased operations in 1935. The highway was originally named for George N. Palmer, a community leader in Seat Pleasant. MD 704 was temporarily marked as Temp US 50 when John Hanson Highway's western terminus was at MD 704 between 1959 and the highway's completion west to Washington in the early 1960s. The state highway was expanded to a divided highway from Glenarden to just east of John Hanson Highway around 1964 and within Seat Pleasant by 1970. MD 704 was expanded to a divided highway from Seat Pleasant to Glenarden around 1970. MD 704 was renamed for Martin Luther King, Jr. between 1986 and 1999. The final two-lane portion of the state highway, from just east of US 50 to MD 450, was expanded to a six-lane divided highway in 2000.

The entire route is in Prince George's County.