Mary DeSoto was a Human serving in Starfleet during the 24th century.
Many of her family served in Starfleet, including her great uncle, Robert DeSoto.
She was one of nine survivors after the ship was destroyed during the Battle of Tyra, and was incarcerated at the Hekiss Prisoner of War Camp for several months. She was the senior Starfleet medical officer there. She received a commendation for her work at the POW Camp. ("Familiar Faces")
On stardate 51905.4 she was part of an away team to the moon of Perdition to rescue stranded crew members of the USS Potemkin and IKS Krohtal. ("Perdition's Flames")