Maryland Route 191 (MD 191) is a state highway in the U.S. state of Maryland. The route runs 7.16 mi (11.52 km) from Maryland Route 190 (River Road) in Potomac to Maryland Route 185 (Connecticut Avenue) in Chevy Chase.

Maryland Route 191 begins at Maryland Route 190 (River Road) in Potomac as Bradley Boulevard, a two-lane road with a speed limit of 35 mph (56 km/h). Bradley Boulevard continues as an unnumbered road on the other side of the intersection; that road was formerly part of MD 191. The road heads east through forests and affluent residential areas. After intersecting Kentsdale Drive and Aldershot Drive, MD 191 crosses Cabin John Creek. The road then intersects Seven Locks Road, an arterial that links Cabin John and Rockville. After crossing Seven Locks Road, MD 191 expands to a four-lane divided highway for its crossing of I-495 (Capital Beltway). After crossing the interstate with no access, the road becomes a two-lane road again.

MD 191 continues through affluent residential areas in Bethesda. Shortly after crossing the Capital Beltway, the road intersects Burdette Road and Fernwood Road. MD 191 then turns southeast after an intersection with Huntington Parkway. Passenger vehicles may use Huntington Parkway to access Maryland Route 187 (Old Georgetown Road). As the road enters a higher density residential area, the speed limit drops to 30 mph (48 km/h). The road then intersects Maryland Route 188 (Wilson Lane). Further to the east, MD 191 expands to a six-lane divided suburban arterial immediately before the intersection with Maryland Route 614 (Goldsboro Road).

After passing MD 614, MD 191 crosses Glenbrook Road and Fairfax Road. Heading south on either road leads to Little Falls Parkway, which parallels Little Falls Branch. Passenger vehicles may use Little Falls Parkway to access MD 191 and Maryland Route 396 (Massachusetts Avenue). After crossing Fairfax Road, MD 191 enters an area of shopping centers and apartment buildings. Within this densely-populated area, the route intersects Arlington Road, which provides access to downtown Bethesda. After passing under the railroad-type overpass that carries the Capital Crescent Trail, MD 191 intersects Hillandale Road and Leland Street, the latter of which was formerly Maryland Route 82. The road then reduces to a four-lane divided suburban street with parking lanes. Shortly after passing more apartment buildings, the road meets Maryland Route 355 (Wisconsin Avenue) and changes its name to Bradley Lane on the east side of the intersection.

The Bradley Lane portion of MD 191 is a two-lane road with a speed limit of 25 mph (40 km/h). The road is fronted on the south by Chevy Chase Country Club and on the north by residences in the town of Chevy Chase. MD 191 comes to an end at Maryland Route 185 (Connecticut Avenue). Bradley Lane continues east as a municipally-maintained road on the other side of the intersection to Maryland Route 186 (Brookville Road).

Maryland Route 191 was entirely paved by 1927, although the Bradley Lane portion was a state aid road paved in macadam. At that time, MD 191 extended west from its current terminus along Bradley Boulevard and what is now Persimmon Tree Road and Persimmon Tree Lane to MacArthur Boulevard in Cabin John. The 1939 Maryland state highway map shows MD 191 assigned to the Persimmon Tree Road and Bradley Boulevard portions. It is not clear when the Bradley Lane portion graduated from a state aid road to the state road system. The part of MD 191 west of MD 190 was removed from the state road system in 1999.

The entire route is in Montgomery County.