Maryland Route 165 is a state highway in the U.S. state of Maryland. The state highway runs 20.38 miles (32.80 km) from Baldwin north to the Pennsylvania state line in Cardiff, where the highway continues as Pennsylvania Route 74. MD 165 passes through western and northern Harford County, where it connects the communities of Fallston, Jarrettsville, Pylesville, and Whiteford. The state highway was constructed as part of MD 24 through Pylesville and Whiteford in the late 1910s and early 1920s. MD 165 from Baldwin through Jarrettsville to west of Pylesville was built in the late 1920s and early 1930s. When MD 24 was rerouted in 1933, MD 165 was extended along that highway's old routing through Pylesville and Whiteford, much of which was relocated in 1960.

Pennsylvania Route 74 is a 96.4-mile-long (155.1 km) north–south state highway located in central Pennsylvania. The southern terminus of the route is at the Mason–Dixon line southwest of Delta, where the road continues into Maryland as Maryland Route 165. The northern terminus is at PA 75 south of Port Royal.