The Upper East Side is a neighborhood in the borough of Manhattan in New York City, between Central Park/Fifth Avenue, 59th Street, the East River, and 96th Street. The area incorporates several smaller neighborhoods, including Lenox Hill, Carnegie Hill, and Yorkville. Once known as the Silk Stocking District, it is now one of the most affluent neighborhoods in New York City.

Neighborhood boundaries in New York City are not officially set, but according to the Encyclopedia of New York City, the Upper East Side is bounded by 59th Street in the south, 96th Street on the north, Fifth Avenue to the west and the East River to the east. The AIA Guide to New York City extends the northern boundary to 106th Street near Fifth Avenue.

The area's north-south avenues are Fifth, Madison, Park, Lexington, Third, Second, First, York, and East End Avenues, with the latter running only from East 79th Street to East 90th Street. The major east-west streets are 59th Street, 72nd Street, 79th Street, 86th Street and 96th Street.

Some real estate agents use the term "Upper East Side" instead of "East Harlem" to describe areas that are slightly north of 96th Street and near Fifth Avenue, in order to avoid associating these areas with the negative connotations of the latter, a neighborhood which is generally perceived as less prestigious.