The Beaver Kill, sometimes written as the Beaverkill or Beaverkill River, is a tributary of the East Branch of the Delaware River, approximately 44 miles (71 km) long, in the U.S. State of New York. The kill drains a 300-square-mile (780 km2) area of the Catskill Mountains and has long been celebrated as one of the most famous trout streams in the United States.