Light Vessel Number 83 (LV-83) Swiftsure is a lightship and museum ship owned by Northwest Seaport in Seattle, Washington. Launched in 1904 at Camden, New Jersey and in active service until 1960 after serving on all five of the American west coast's lightship stations, it is the oldest surviving lightship in the United States, the only one still fitted with its original steam engine, and the last lightship with wooden decks. LV-83 was designated a National Historic Landmark in 1989, and has been undergoing major restoration since 2008.

A lightvessel, or lightship, is a ship that acts as a lighthouse. They are used in waters that are too deep or otherwise unsuitable for lighthouse construction. Although some records exist of fire beacons being placed on ships in Roman times, the first modern lightvessel was off the Nore sandbank at the mouth of the River Thames in London, England, placed there by its inventor Robert Hamblin in 1734. The type has become largely obsolete; lighthouses replaced some stations as the construction techniques for lighthouses advanced, while large, automated buoys replaced others.