Lake Needwood is a 75-acre (300,000 m2) reservoir in Derwood, Maryland, United States. Located east of Rockville, in the eastern part of Montgomery County, it is situated on Rock Creek. The lake was created by damming Rock Creek in 1965 with the goal of providing flood control and reducing soil erosion. Lake Needwood also protects the water quality of the creek by functioning as a retention basin to trap sediment from storm-water runoff.

Derwood is an unincorporated area and census-designated place in east-central Montgomery County, Maryland, United States. It lies just north of Rockville, southeast of Gaithersburg, southwest of Olney, and northwest of the greater Silver Spring area. Derwood was originally "Deer Park" and was then "Deer Wood" before getting its current name.