Mary Thistlethwaite (also spelt as Thistlethwayte; née Foxcrofte; 1520 – ????) was the 14th great-grandmother of Cometan, classified as one of Cometan’s distant paternal ancestors in the McKerney family line. Born in Dent, Yorkshire (in modern-day Cumbria), Mary was the mother of Alexander Thistlethwaite. Mary’s father was named Samuel Foxcroft, but the identity of her mother remains unknown.
In Cometanic ancestry, Mary is categorised as part of the 16th generation retrograde, classifying her as a distant ancestor of Cometan.