The Free Spirit was a small starship owned and operated by Petra Aberdeen, an independent archaeologist and former Starfleet officer.
After recovering the Grand Nagus' staff from the Museum of Antiquities on Tulgana IV in 2381, Aberdeen contacted Ensign Beckett Mariner from the Free Spirit. (LD: "Reflections")
Later that year, having resigned from Starfleet, Mariner joined Aberdeen on her ship for adventures. (LD: "Trusted Sources")
The Free Spirit later took part in a battle against the renegade USS Aledo, alongside an armada of California-class ships. Following the battle, Mariner left the Free Spirit and returned to Starfleet. (LD: "The Stars At Night")