The Alsea Bay Bridge is a concrete arch bridge that spans the Alsea Bay on U.S. Route 101 (US 101) near Waldport, Oregon.

There have been two bridges on this site.

The first bridge was designed by Conde McCullough and opened in 1936. It was a 3,011-foot-long (918 m) reinforced-concrete combination deck and through arch bridge.

The hostile environment caused significant corrosion to the steel reinforcements. In 1972 the Oregon Department of Transportation began projects aimed at extending the life of the bridge. By the mid-1980s it was decided to replace the bridge rather than continue costly rehabilitation efforts. The first bridge was demolished in 1991. Construction of the second bridge, designed by HNTB, began in 1988, and it was opened in the fall of 1991 at a cost of $42.4 million. The bridge is 2,910 ft (890 m) in total length, with a 450 ft (140 m) main span that provides 70 ft (21 m) of vertical clearance. The bridge has a latex concrete deck and the piers are significantly thicker than normal in an attempt to thwart corrosion. Its life expectancy is 75 to 100 years.

• Transport portal
• Engineering portal
• Oregon portal
• List of bridges documented by the Historic American Engineering Record in Oregon
• List of bridges on U.S. Route 101 in Oregon

• Photos
• Alsea Bay Bridge (1936) at Structurae
• Alsea Bay Bridge (1991) at Structurae
• Alsea Bay Bridge Interpretive Center
• Historic American Engineering Record (HAER) No. OR-14, "Alsea Bay Bridge, Spanning Alsea Bay at Oregon Coast Highway, Waldport, Lincoln County, OR", 39 photos, 7 color transparencies, 2 measured drawings, 10 data pages, 3 photo caption pages
• HAER No. OR-64, "New Alsea Bay Bridge", 2 photos, 1 photo caption page
• Alsea Bay Bridge Photo Gallery