William Floyd House, also known as Nicholl Floyd House and Old Mastic House, was a home of William Floyd, a signer of the United States Declaration of Independence, in Mastic Beach, New York. It was his home from 1734 until 1803. This home is distinct from Gen. William Floyd House, his later home in Westernville, New York, that is also on the National Register and which was designated a National Historic Landmark. The house is owned by the National Park Service as part of Fire Island National Seashore, although it's not on Fire Island itself.