Clemence de Sandbach (1210 – c.1259) was the 29th great-grandmother of Cometan, classified as one of Cometan’s medieval paternal ancestors in the Taylor family line.

Little is known of Clemence’s life except for that she was born in Sandbach, Cheshire and that she was the wife of Roger de Sandbach. She gave birth to at least one son named Richard, whom connects her to the Cometanic ancestry. The identities of Clemence’s parents as well as exact dates of her birth and death remain unknown. 

In Cometanic ancestry, Clemence de Sandbach is categorised as part of the 31st generation retrograde, and because she was born before 1453, she is classified as a medieval ancestor of Cometan, a title that is rarely bestowed.