Lake Oswego Railroad Bridge, Railway bridge in Lake Oswego, Oregon, United States

The Lake Oswego Railroad Bridge is a 1,378-foot truss bridge over the Willamette River between Lake Oswego and Oak Grove. Two 298-foot through truss spans carry the rail deck across the river, with a 668-foot open-deck trestle on the Oak Grove side and a 60-foot trestle plus a 50-foot plate girder approach span on the Lake Oswego side.

Built in 1910 by the Beaverton and Willsburg Railroad, a Southern Pacific subsidiary, the bridge answered Portland planners' wish for an eastside railway bypass keeping trains out of downtown. Robert Wakefield, later involved with the Steel Bridge, was the builder. Union Pacific took ownership with its 1996 acquisition of Southern Pacific.

The bridge's name has shifted with its owners: it was the Southern Pacific Railroad Bridge at Lake Oswego until Union Pacific absorbed Southern Pacific in 1996, and it is now also called the Union Pacific Railroad Bridge at Lake Oswego. Portland-area commuters have campaigned to open it to passenger trains or bicycles, though it carries only freight today.

Train service on the bridge is now limited, with the Portland and Western Railroad operating occasional freight movements. The structure can be viewed from nearby riverbank access points and parks along the Willamette.

The west approach span, a 50-foot deck plate girder, was built in 1900 and moved to this crossing in 1931, so part of the bridge predates the 1910 truss spans. The 60-foot open-deck trestle on the same bank followed in 1934.