Ruby Sunday

Ruby Sunday is a fictional character in the British science fiction television series Doctor Who, portrayed by Millie Gibson. She was created by Russell T Davies for the show's fourteenth series, starting with the Christmas special, "The Church on Ruby Road" (2023), Ruby serves as the companion to the Fifteenth Doctor (Ncuti Gatwa), an incarnation of the alien time traveller known as the Doctor. Ruby is a foundling, left on the doorstep of a church by her mother as a baby, with her mother's identity being unknown. After an encounter with the Doctor, the pair travel through time and space in multiple episodes, all while Ruby attempts to discover the identity of her birth mother. This eventually culminates in the two-part finale of the season, "The Legend of Ruby Sunday" and "Empire of Death" (both 2024), in which Ruby discovers the identity of her birth mother as Louise Miller (Faye McKeever), an ordinary woman, and the two reunite. Ruby departs to spend time with her family.

Gibson was cast as Ruby in 2022. She characterised Ruby as being a positive, selfless character, who had a strong bond with the Doctor. Her arc of finding out the identity of her mother was inspired by the Star Wars film series character Rey, a character believed to be a nobody until she was revealed to be a descendent of the character Emperor Palpatine. Davies wanted to subvert the trope of a character secretly being "special", or having important parentage, and thus made Ruby and her mother normal people.

Ruby returned in the season fifteen episode "Lucky Day" (2025), in which she is struggling with post-traumatic stress disorder following her time with the Doctor. She gets into a relationship with podcaster Conrad Clark (Jonah Hauer-King), who is secretly using her to discredit the military organization UNIT. Gibson described her appearance in this episode as showing a more "grown up" character, being less open than she had been in the prior season. Following "Lucky Day", she appears in the two-part season finale: "Wish World" and "The Reality War" (both 2025), where she aids the Doctor in saving Earth from both Conrad and the Doctor's old enemy The Rani.

Ruby has received a largely positive reception from critics, with Gibson's performance being praised.