The Olive-sided Flycatcher, Contopus cooperi, is a passerine bird. It is a medium-sized tyrant flycatcher.

Adults are dark olive on the face, upperparts and flanks. They have light underparts, a large dark bill and a short tail.

Their breeding habitat is coniferous woods across Canada, Alaska and the northeastern and western United States, and other types of wooded area in California. Olive-sided Flycatchers are abundant in early postfire landscapes that have burned at high severity. The female usually lays 3 eggs in a shallow open cup nest on a horizontal tree branch. The male defends a large area around the nesting territory. Both parents feed the young birds.

These birds migrate to Central America and the Andes region of South America.

They wait on a perch at the top of a tree and fly out to catch insects in flight.

The song is a whistled quick-three beers. The call is a rapid pip pip pip.

The numbers of this bird are declining, probably due to loss of habitat in its winter range.

Note on taxonomy. Contopus borealis is a junior synonym of Contopus cooperi, according to the 1997 AOU checklist, quoted by BISON. The name of this species is listed as Contopus borealis in many older guides.

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