The 2004 USS Nimitz UAP encounter involved multiple unidentified aerial vehicles (UAPs) detected by the USS Princeton's radar for several days in November 2004 off the coast of Southern California/Baja Peninsula. These objects were tracked descending rapidly from high altitudes (over 80,000 feet).

On November 14, Cmdr. David Fravor and Lt. Cmdr. Alex Dietrich were diverted to investigate a radar contact. They visually observed a white, Tic-Tac shaped object, approximately 45 feet long, with no visible wings, engines, or propulsion, moving erratically over an area of disturbed water. Four crew members saw it visually.

Fravor reported the object appeared aware of their presence and mirrored his movements. When he attempted to intercept, it accelerated instantaneously and disappeared from view. The USS Princeton radar reacquired the object 60 miles away seconds later, indicating performance vastly superior to advanced fighter aircraft. Another crew later filmed the object with infrared (FLIR1 video), which showed no typical exhaust plume.

The object's maneuvers, including descending 80,000 feet in less than a second (implying speeds > 45,000 mph and > 2,000g based on standard models), are beyond the limits of known physics and terrestrial technology. Such forces would be lethal to human occupants. The UAP also demonstrated stealth against radar and appeared to be able to visually 'cloak'. It was difficult to track continuously. The possibility of undersea operation was considered, though a submarine operating nearby detected nothing unusual.

Witnesses included multiple pilots, weapons system officers, and radar operators across several ships and aircraft. Despite the dramatic encounter, there was no official investigation immediately afterward, and crew members reported facing ridicule.

The incident was later investigated as part of the Advanced Aviation Threat Identification Program (AATIP). An AATIP report concluded the "Anomalous Aerial Vehicle" was of unknown origin, not US or foreign technology, and possessed capabilities far exceeding existing or near-future aircraft. Explaining the object's performance may require entirely new forms of physics not yet discovered. Speculative concepts like warp drive, which manipulates spacetime, have been considered as theoretical possibilities, and research into such areas was part of AATIP-related work. Fravor testified about the event to Congress in 2023.

Skeptics offer alternative explanations such as radar glitches, optical illusions, camera effects (glare, parallax, bokeh), weather balloons, or advanced drones. However, witnesses like Fravor dismiss these explanations, while Dietrich is wary of jumping to extraterrestrial conclusions.