Lost Lake is a lake in Mount Hood National Forest 16.2 kilometres (10.1 mi) northwest of Mount Hood in Hood River County in the U.S. state of Oregon. It is 34.4 kilometres (21.4 mi) southwest of Hood River, a 26.4-mile (42.5 km) drive.
The lake is bounded on the east by 4,468-foot (1,362 m) Lost Lake Butte and on the southwest by 4,556-foot (1,389 m) Preachers Peak. The lake is fed by three unnamed intermittent creeks from Lost Lake Butte, and Inlet Creek from Preachers Peak. The lake maintains a very consistent level via an outlet at the north tip, the source of Lake Branch Hood River, a tributary of West Fork Hood River. It is the second-deepest lake in Mount Hood National Forest after Wahtum Lake at 167 feet (51 m).