Klamath Basin National Wildlife Refuge Complex, National wildlife refuge complex in northern California and southern Oregon

The Klamath Basin National Wildlife Refuge Complex is a US Fish and Wildlife Service preserve of six refuges near Klamath Falls, Oregon: Bear Valley, Klamath Marsh and Upper Klamath in Oregon, and Lower Klamath, Tule Lake and Clear Lake in California. Lower Klamath, established in 1908, covers 46,900 acres of shallow freshwater marsh, open water, grassy uplands and croplands; Clear Lake holds about 20,000 acres of open water within 46,460 acres.

The first area was created in 1908 by Theodore Roosevelt and was the earliest waterfowl refuge in the United States. It was later expanded to incorporate additional habitats and protect more species.

The refuges are managed by the U.S. Fish and Wildlife Service, with agricultural and water programs coordinated under an agreement with the Bureau of Reclamation. Farming and wetland conservation therefore share the same land and water: croplands on the refuges are managed to provide feeding and nesting habitat for waterfowl. The Klamath Refuge has been called "the heartbeat of the Pacific Flyway".

The visitor center in Tulelake provides exhibits and information along with access to walking trails and observation platforms. The best time to visit is during spring and fall migration seasons when millions of birds pass through the area.

Bear Valley Refuge, added in 1978, protects a winter night roost for bald eagles in old-growth ponderosa pine, incense-cedar, white fir and Douglas-fir. The refuge complex has recorded 433 bird species, and each fall about three-quarters of the Pacific Flyway's waterfowl pass through, which earned it the name "heartbeat of the Pacific Flyway."