Bellefields is a manor house located in Croom, Prince George's County, Maryland. It was constructed about 1720. It is a brick structure in Flemish bond with random glazed headers, and two stories over a high basement. The structure is rectangular, with gabled roof sections, paired interior end chimneys, a front center entrance, wide raised belt course above the first floor, flat arched openings, and flanking symmetrical single-story wings. It is in the Georgian style. It was the home of Patrick Sim, Scottish immigrant and of his son, Col. Joseph Sim, Maryland patriot.