Huey P. Long Bridge, Railroad and highway bridge in Baton Rouge, United States.

The Huey P. Long Bridge carries US 190 and a single Kansas City Southern rail line across the Mississippi between East and West Baton Rouge Parish. Its main span is a symmetric cantilever truss 1,014 m long and about 27 m wide, resting on six reinforced concrete piers with spans of 149, 259, 198, 259 and 149 m. The track runs inside the truss, 9.8 m between chord centres, while the roadways sit on brackets outside it; steel trestle approaches extend 1,093 m east and 1,615 m west.

Opened in August 1940, the bridge was named for governors Huey P. Long and Oscar K. Allen, though its official name was shortened in 1974. It carried US 190 and a Kansas City Southern rail line, and until April 1968 it was Baton Rouge's only Mississippi crossing. A 2012–2016 overhaul costing nearly 100 million USD repaired the substructure and steel truss and stripped the old lead paint.

The bridge is named after two Louisiana governors, Huey P. Long and Oscar K. Allen, and locals simply call it the old bridge, which reflects its importance in the region's past.

The deck carries four narrow lanes of US 190 (Airline Highway) plus one Kansas City Southern rail track, with roughly 28,500 vehicles and 5 to 6 trains daily. Lanes ice over in cold weather, and the girder foundations on both railroad approach spans show hairline cracks. The eastbound approach passes a dock still bearing scars from a 1945 truck accident.

The structure had an unusual color history, originally painted blue before becoming orange in the 1960s due to aluminum oxide dust from a nearby plant. The color was changed to gray in 2016, giving the bridge a different appearance than in earlier decades.