My Lady's Manor is a national historic district at Monkton, Baltimore County and Jarrettsville, Harford County, Maryland, United States. It is a rural or agricultural area, with one village, Monkton. Monkton first developed around a water-powered grist mill and later became a station on the Northern Central Railway. The 10000 acre manor itself was established in 1713. Over 60 principal structures, plus numerous important outbuildings associated with them, are included in the district. It was added to the National Register of Historic Places in 1978.