Maryland Route 27 is a state highway in the central part of the U.S. state of Maryland.

MD 27, also known as Ridge Road and Manchester Road (at Northern Point), begins in Germantown at MD 355. Despite signage at I-270 Exit 16, the route does not actually reach the Interstate.

The route runs north through Germantown and Damascus, crossing Frederick, Howard and Carroll counties into Mt. Airy. Remaining in Carroll County, the route runs north, intersecting MD 26 in Taylorsville and eventually reaches Westminster. After running through downtown Westminster and crossing MD 140, the route continues north and ends in Manchester at MD 30.

The route was originally designated Maryland Route 29 in 1933, with the original route of U.S. Route 29 via Ashton being designated Maryland Route 27. After US 29's arrival in 1934, the two routes swapped numbers, with MD 29 becoming MD 27, and MD 27 becoming MD 29 (and thus being promoted to US 29 without conflict).

At one time, all of MD 27 north of Westminster, as well as a small piece of the former route northeast of Manchester, was part of MD 31.