The Bronx is a borough of New York City, coextensive with Bronx County, in the state of New York. It is south of Westchester County; north and east of the New York City borough of Manhattan, across the Harlem River; and north of the New York City borough of Queens, across the East River. The Bronx has a land area of 42 square miles (109 km2) and a population of 1,472,654 in the 2020 census. If each borough were ranked as a city, the Bronx would rank as the ninth-most-populous in the U.S.

Of the five boroughs, it has the fourth-largest area, fourth-highest population, and third-highest population density. It is the only borough of New York City not primarily on an island. With a population that is 54.8% Hispanic as of 2020, it is the only majority-Hispanic county in the Northeastern United States and the fourth-most-populous nationwide. The Bronx is divided by the Bronx River into a hillier section in the west, and a flatter eastern section. East and west street names are divided by Jerome Avenue. The West Bronx was annexed to New York City in 1874, and the areas east of the Bronx River in 1895.