Maid Marian

 was the lover of Robin Hood.

According to one account, Marian met Ian Chesterton and Susan when they tried to rescue her from the dungeon of the Sheriff of Nottingham. After she was rescued, she promised to keep the dead Robin's memory alive. Her accounts of him became the legends of his adventures. (PROSE: The Thief of Sherwood)

Another account suggested she was the ward of a man named Quayle, who was killed when she was taken prisoner by the Sheriff of Nottingham. After helping the Twelfth Doctor defeat the Sheriff's robots, he reunited her with Robin Hood. (TV: Robot of Sherwood)

Alternate timeline
In an alternate timeline where Polly Wright was manipulated into interfering with temporal nexus points, Polly convinced Marian to stand up to Robin. (PROSE: That Time I Nearly Destroyed the World Whilst Looking for a Dress)

Behind the scenes
For her appearance in Robot of Sherwood, Marian was credited as "Quayle's Ward" to keep her identity a secret, a sub-plot within the episode being Robin Hood's search for her.