New York's 21st congressional district is a congressional district for the United States House of Representatives that is represented by Republican Elise Stefanik.

The district is rural and it includes the cities of Ogdensburg, Glens Falls, and Plattsburgh.The district includes most of the Adirondack Mountains and the Thousand Islands region. It borders Vermont to the east and Canada to the north. It also includes Fort Drum of the U.S. Army.

From 2003 to 2013, the district with that number contained most of the Capital District of New York. It included all or parts of Albany, Fulton, Montgomery, Rensselaer, Saratoga, Schenectady, and Schoharie counties. It contained the cities of Albany, Schenectady, Troy, Amsterdam, Cohoes, Watervliet, Gloversville, and Johnstown. Up until 1980, the 21st district was located in Upper Manhattan (including parts of Harlem and Washington Heights), and The Bronx.

From 2013 to present: Clinton, Essex, Franklin, Fulton, Hamilton, Herkimer, Lewis, Montgomery, Schoharie, St. Lawrence, Warren, and Washington counties, and parts of Jefferson, Otsego, and Rensselaer counties.

In New York State electoral politics there are numerous minor parties at various points on the political spectrum. Certain parties will invariably endorse either the Republican or Democratic candidate for every office, hence the state electoral results contain both the party votes, and the final candidate votes (Listed as "Recap").

• List of United States congressional districts
• New York's congressional districts
• United States congressional delegations from New York