Rock Creek is also the name of several cities in the United States: Rock Creek, Alabama, Rock Creek, Minnesota, Rock Creek, Ohio, and Rock Creek, Wisconsin.

Rock Creek is a free-flowing tributary of the Potomac River, which empties into the Atlantic Ocean via Chesapeake Bay. The creek is approximately 33 miles (53.1 km) long, with a drainage area of about 76.5 mi² (198 km²). The last quarter mile (402 metres) of the creek is affected by tidal activity.

The creek rises from a spring near Laytonsville in Montgomery County, Maryland, and joins with the Potomac near Georgetown in Washington, DC. About 9 miles (14.5 km) of the creek flow though Rock Creek Park in Washington, where it is fed by eight small creeks — including Piney Branch, Pinehurst Branch, Broad Branch, Soapstone Branch, and Luzon Branch — and numerous storm sewers.

About 21 percent of the creek's watershed is in Washington, DC. Total land usage in the watershed is 896 acres (3.6 km²) of wetlands or water, 22,272 acres (90 km²) of residential and commercial areas, 15,488 acres (63 km²) of forest or grasslands, and 10,304 acres (42 km²) of agricultural areas.

The creek has a fairly steep gradient with rapid changes in elevation.

In December 2003, the National Park Service annouced plans to remove or bypass eight fish barriers in the creek, including adding a fish ladder to bypass the historic 1905 Peirce Mill Dam, modifying historic fords, and removing abandoned sewage lines and fords. The effort is designed to restore American shad, river herring, and other migratory fish to the creek and their historic upriver spawning grounds.