Foundry Branch is a tributary stream of the Potomac River in Washington, DC. The historic headwaters of the stream originate in the Tenleytown area in Northwest Washington, however at present the section of the stream north of Massachusetts Avenue is hydrologically separated from the lower section and runs through a large stormwater pipe under the daylighted portion. The daylight portion of the stream can be seen south of Massachusetts Avenue, in Glover-Archbold Park, and the stream continues to the Potomac, which drains to the Chesapeake Bay.