Maryland Route 355 (MD 355) is a north–south road in western central Maryland in the United States. The southern terminus of the route is at the Washington, D.C. border in Friendship Heights, Montgomery County, where it continues south as Wisconsin Avenue into Washington. The northern terminus is just north of an overpass with Interstate 70 (I-70) and U.S. Route 40 (US 40) in the city of Frederick in Frederick County, where the road continues north through Frederick towards MD 26. MD 355 serves as a major thoroughfare through Frederick and Montgomery counties, passing through Bethesda, Rockville, Gaithersburg, Germantown, Clarksburg, Hyattstown, Urbana, and Frederick, roughly parallel to I-270. The southern portion of the route from the D.C. border to Germantown is a suburban four- to six-lane divided highway lined with many businesses. North of Germantown, the route is predominantly a two lane rural road until it reaches Frederick, where it passes through commercial areas in the southern part of the city.