|Country||United States of America|
|Time zone||Eastern (EST) (UTC-5)|
|• Summer (DST)||EDT (UTC-4)|
Monkton is an unincorporated community in northern Baltimore County, Maryland, United States. It has a population of about 4,856 people. It is 35 square miles (91 km2) in area, with approximately 138 inhabitants per square mile (53/km2). As an unincorporated area, Monkton has no legally defined boundaries, and its postal ZIP code (21111) includes a portion of adjacent Harford County.
East of Monkton is an area named "My Lady's Manor", known for its horse farms, sprawling countryside, and old, stately homes set back from the country roads. In 1713, Charles Calvert, 3rd Baron Baltimore, decreed 10,000 acres (40 km²) for himself. He made a gift of this land to his fourth wife, christening the estate "My Lady's Manor." It was added to the National Register of Historic Places in 1978. Also listed on the National Register are the Corbett Historic District and St. James Church.
- Thoroughbred horse racing trainer Helen Pitts, who was born and raised here.
- Foxhall P. Keene, a thoroughbred owner/breeder and Gold Medallist in Polo at the 1900 Summer Olympics.
- Harvey S. Ladew (1887–1976), American fox hunting and topiary enthusiast
- Peter Angelos, attorney and owner of the Baltimore Orioles
- Jim McKay, longtime host of ABC television's Wide World of Sports and Olympics commentator
- Major League Baseball pitcher A.J. Burnett
- Atlanta Braves outfielder Nick Markakis.
- Wine critic Robert Parker
Filmmaker Erik Kristopher Myers shot the 2013 thriller Roulette (film) at various public and private locations on York Road and Mt. Carmel Road, including the GBMC, the NCR Trails, and The Milton Inn.
The community was formerly served by the Northern Central Railway division of the Pennsylvania Railroad from the mid-19th century until the line's abandonment in 1972 and conversion to a hiking trail, the Northern Central Railroad Trail. The original Monkton station still remains.