Big Tujunga Dam is a concrete arch dam in Los Angeles County, California, spanning Big Tujunga Creek northeast of Sunland. Completed in 1931 by the Los Angeles Department of Water and Power, it serves mainly for flood control. The dam was originally planned as one of several similar flood-control dams inside Big Tujunga Canyon and was thus referred to as Big Tujunga Dam No. 1 until the large Hansen Dam was completed in 1940, eliminating the need for the other components of the original project.
Its reservoir is called Big Tujunga Reservoir, and has a capacity of 5,960 acre·ft (7,350,000 m3). Although it is located inside the Angeles National Forest, public access to the lake is forbidden. The water is kept at a low level except during the rainy season. Because of the small storage capacity of the reservoir, it has filled completely with sediment on several occasions, including 1969 and 2011; as a result frequent dredging is required to keep the dam operational.