Double Pipe Creek, sometimes called Pipe Creek, is a major tributary of the Monocacy River in Carroll County and Frederick County in Maryland, located several miles north and west of Westminster. The creek is only 1.6 miles (2.6 km) long, but is formed by the confluence of two much longer streams, Big Pipe Creek and Little Pipe Creek.
The creek's watershed extends as far east as Manchester, Maryland, and includes the towns of Union Bridge, Taneytown, New Windsor and Westminster. The main stem of the creek is formed from the confluence of Big Pipe Creek, 31.6 miles (50.9 km) long, with headwaters near Manchester; and Little Pipe Creek, 24.9 miles (40.1 km) long, with headwaters in Westminster. From the confluence, near Detour, Maryland (39°36′04″N 77°16′13″W / 39.6012°N 77.2703°W), Double Pipe flows west for 1.6 miles (2.6 km) to its mouth at the Monocacy, which drains to the Potomac River. The watershed area of Double Pipe Creek is 192.6 square miles (499 km2).
Tributaries include Bear Branch, Big Pipe Creek, Little Pipe Creek, Meadow Branch and Sam’s Creek. Double Pipe Creek, the portion of Little Pipe Creek west of Union Bridge, and the western section of Sam's Creek form part of the legal boundary between Frederick County and Carroll County.