Nantucket Sound is a roughly triangular area of the Atlantic Ocean offshore from the U.S. state of Massachusetts. It is enclosed by Cape Cod on the north, Nantucket on the south, and Martha's Vineyard on the west; between Cape Cod and Martha's Vineyard it is connected to the Vineyard Sound. Ports on Nantucket Sound include Nantucket and Hyannis, Massachusetts.

Nantucket Sound has recently become a subject of controversy as a result of a plan to build the United States' first offshore wind farm there.