The Manhattan Bridge is a suspension bridge that crosses the East River in New York City, connecting Lower Manhattan at Canal Street with Downtown Brooklyn at the Flatbush Avenue Extension. Designed by Leon Moisseiff, the bridge has a total length of 6,855 ft (2,089 m). The bridge is one of four vehicular bridges directly connecting Manhattan Island and Long Island; the nearby Brooklyn Bridge is just slightly farther west, while the Queensboro and Williamsburg bridges are to the north.

The bridge was proposed in 1898 and was originally called "Bridge No. 3" before being renamed the Manhattan Bridge in 1902. Foundations for the bridge's suspension towers were completed in 1904, followed by the anchorages in 1907 and the towers in 1908. The Manhattan Bridge opened to traffic on December 31, 1909, and began carrying streetcars in 1912 and New York City Subway trains in 1915. The eastern upper-deck roadway was installed in 1922. After streetcars stopped running in 1929, the western upper roadway was finished two years later. The uneven weight of subway trains crossing the Manhattan Bridge caused it to tilt to one side, necessitating an extensive reconstruction between 1982 and 2004.

The Manhattan Bridge was the first suspension bridge to use a Warren truss in its design. It has a main span of 1,480 ft (451 m) between two 350-foot (110 m) suspension towers. The deck carries seven vehicular lanes, four on an upper level and three on a lower level, as well as four subway tracks, two each flanking the lower-level roadway. The span is carried by four main cables, which travel between masonry anchorages at either side of the bridge, and 1,400 vertical suspender cables. Carrère and Hastings designed ornamental plazas at both ends of the bridge, including an arch and colonnade in Manhattan that is a New York City designated landmark. The bridge's use of light trusses influenced the design of other long suspension bridges in the early 20th century.

The bridge was the last of the three suspension spans built across the lower East River, following the Brooklyn and Williamsburg bridges. After the City of Greater New York was formed in 1898, the administration of mayor Robert Anderson Van Wyck formed a plan for what became the Manhattan Bridge; these plans were repeatedly revised and were not finalized until after George B. McClellan Jr. became mayor in 1901. From the outset, the bridge was planned to have a central roadway, streetcar tracks, elevated tracks, and sidewalks, and it was to run straight onto an extension of Flatbush Avenue in Brooklyn.

In the earliest plans it was to have been called "Bridge No. 3", but was given the name Manhattan Bridge in 1902. When the name was confirmed in 1904, The New York Times criticized it as "meaningless", lobbied for one after Brooklyn's Wallabout Bay, and railed that the span "would have geographical and historical significance if it were known as the Wallabout Bridge". In 1905, the Times renewed its campaign, stating, "All bridges across the East River are Manhattan bridges. When there was only one, it was well enough to call it the Brooklyn Bridge, or the East River Bridge".

The earliest plans for what became the Manhattan Bridge were designed by R. S. Buck. These plans called for a suspension bridge with carbon steel wire cables and a suspended stiffening truss, supported by a pair of towers with eight braced legs. This design would have consisted of a main span of 1,470 feet (450 m) and approaches of 725 feet (221 m) each. In early 1901, the city government approved a motion to acquire land for a suspension tower in Brooklyn; the city shortly began soliciting bids for the tower's foundations. The contract for the Brooklyn suspension tower was awarded in May 1901.

The caisson under the tower on the Brooklyn side was installed in March 1902; workers excavated dirt for the foundations from within the caisson, a process that was completed in December 1902. Three workers had died while working on the Brooklyn-side tower's caisson. A plan for the bridge was announced in early 1903. Elevated and trolley routes would use the Manhattan Bridge, and there would be large balconies and enormous spaces within the towers' anchorages. Work on the Manhattan caisson had commenced in January 1903; it was towed to position in July, and the caisson work was completed by January 1904. The foundations were completed in March 1904. A $10 million grant for the bridge's construction was granted in May 1904 with the expectation that work on the bridge would start later that year.

The Municipal Art Commission raised objections to one of the bridge's plans in June 1904, which delayed the start of construction. Another set of plans was unveiled that month by New York City Bridge Commissioner Gustav Lindenthal, in conjunction with Henry Hornbostel. The proposal also called for each of the suspension towers to be made of four columns, to be braced transversely and hinged to the bottom of the abutments longitudinally. The same span dimensions from Buck's plan were used because work on the masonry pier foundations had already begun. Additionally, the towers would have contained Modern French detail, while the anchorages would have been used for functions such as meeting halls. Lindenthal's plan was also rejected due to a dispute over whether his plan, which used eyebars, was better than the more established practice of using wire cables. The Municipal Art Commission voted in September 1904 to use wire cables on the bridge.