The USX-1 Defiant is a unmanned warship built as a demonstration project by the Defense Advanced Research Projects Agency (DARPA) and completed in February 2025 and began sea trials in following month. It was first seen in public in March 2025 near the U.S. Navy's Naval Air Station (NAS) Whidbey Island. The ship has an LOA of 180 feet with a 240 metric ton displacement. Defence Shipbuilder Serco oversaw the project.