Nantucket LORAN-C transmitter was a LORAN-C transmitter at Siasconset, Massachusetts. It was built in 1963 with a 625 ft tall mast radiator. It operated in conjunction with the LORAN-A station on Nantucket from 1963 to 1981. It was closed in 2010 when the United States discontinued the Loran system, and officially decommissioned on September 10. The tower was taken down in May 2013.