The Bronx is the northernmost of the five boroughs of New York City. It is geographically north and east of the island and borough of Manhattan to the south and west across the Harlem River; and north of the borough of Queens, across the East River. Of the five boroughs, the Bronx is the only one that has the majority of its area on the U.S. mainland and, with a land area of 42 square miles (109 km2)

The Bronx is divided by the Bronx River into a hillier section in the west, closer to Manhattan, and a flatter eastern section, closer to Long Island. East and west street addresses are divided by Jerome Avenue—the continuation of Manhattan's Fifth Avenue. The West Bronx was annexed to New York City in 1874, and the areas east of the Bronx River in 1895; Bronx County was separated from New York County in 1914.