The USS Yosemite (NCC-19002) was a Federation Oberth-class science vessel that was in service with Starfleet in the late 24th century. It had a total crew complement of only five science officers.
In 2369, the Yosemite was dispatched to the Igo sector to study a plasma streamer between two stars. During this mission, a plasma sample exploded in main engineering and the ship drifted off-course.
Subsequently, the USS Enterprise-D was sent to determine the Yosemite's fate. However, an away team found the vessel empty, save for the body of the chief engineer, Lieutenant Joshua Kelly, who died from exposure to high-energy plasma. After Lt. Reginald Barclay, who was part of the Enterprise away team, claimed to see alien lifeforms while beaming between the two ships, it was found that he had been infected by quasi-energy microbes from the plasma streamer, which had also caused the explosion on the Yosemite. The remaining four Yosemite crewmembers were later discovered suspended in the transporter, and were rescued with the aid of Lt. Barclay. (TNG: "Realm of Fear")
Later that year, while under the mind control of interrogators on the planet Tilonus IV, Commander William T. Riker believed that he met a woman named "Commander Bloom," who was first officer of the Yorktown, at the Tilonus Institute for Mental Disorders. She told him that the Tilonians had captured a crewman from the Yosemite named Sanders. According to her, the doctors had done something to his mind. The commander believed that the doctors were removing neurochemicals from their brains, and she thinks this was what happened to Sanders. (TNG: "Frame of Mind")
The Yosemite was later recovered and traveled from New Brooklyn IX to visit starbase Deep Space 9 on stardate 47552.9, while under the command of Captain J. Swift. (DS9: "Whispers")