Main Street Bridge, Vertical-lift road bridge in Downtown Jacksonville, United States

The Main Street Bridge, officially the John T. Alsop Jr. Bridge, is a light-blue steel vertical-lift bridge over the St. Johns River in Jacksonville. Its two steel towers rise above a four-lane roadway with a double yellow center line, and lattice-braced posts and horizontal girders form repeated rectangular openings. A sign on the upper crossbeam reads "JOHN T. ALSOP, JR. BRIDGE"; below it, a smaller sign reads "CLEARANCE 16".

Construction began in 1938 under the Mount Vernon Bridge Company after the War Department permitted it in 1936, and the bridge opened on July 17, 1941, at a cost of $1.5 million. It was named for former mayor John T. Alsop Jr. in 1957. An $11 million renovation in 2014 upgraded metal barriers and patched sidewalks.

The bridge serves as a defining landmark along Jacksonville's waterfront and shapes how locals experience the river crossing. People use it daily as a reference point and gather nearby to photograph the water views.

The lift span opens on demand except during restricted hours, 7–8:30 am and 4–6:30 pm, when crossings by water traffic wait. Road traffic uses four lanes signed US 1/US 90, and the 2014 renovation patched the sidewalks for pedestrians.

Of the eight vehicle crossings in the Jacksonville area, four opened with movable spans, but the Main Street Bridge is now the only one still carrying automobile traffic over the St. Johns River that opens for ships. It lifts on demand except during restricted hours, 7–8:30am and 4–6:30pm.