Armonk is a census-designated place (CDP) located in the town of North Castle in Westchester County, New York. As of the 2000 census, the CDP population was 3,461.

Armonk is home to the headquarters of IBM. "Armonk" as a metonym refers to both the headquarters and the company as a whole.

The North Castle Public Library is located in Armonk and is a member of the Westchester Library System.

Smith's Tavern, a local historical site and landmark of the Revolutionary War, is also located in Armonk. Today, it is the home of the North Castle Historical Society.

Armonk is also unique in that there are no national chain stores within the town itself. With the exception of the two gas stations, a supermarket, and three banks, all of the businesses are locally owned and operated.