is an unincorporated community in Baltimore County, Maryland, United States. It has a population of about 4,856 people. It is in area, with approximately . 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.
Thoroughbred horse racing trainer, Helen Pitts was born and raised here. Foxhall P. Keene, a thoroughbred owner/breeder and Gold Medallist in Polo at the 1900 Summer Olympics, maintained an estate here. Several other famous people have made Monkton their home, from Peter Angelos, owner of the Baltimore Orioles, to Jim McKay, longtime host of ABC television's
and a long time Olympic commentator, as well as New York Yankees pitcher, A.J. Burnett.
Monkton was formerly served by the Northern Central Railway division of the Pennsylvania Railroad until its abandonment in 1972 and conversion to a hiking trail. State roads in the area include Maryland Routes 138 and 562.