Sir John Leigh III of Booth’s Hall (c. 1317 – c.1399) was the 25th great-grandfather of Cometan, classified as one of Cometan’s medieval paternal ancestors in the Taylor family line.

Sir John is known to have been born at Booth’s Hall in Norbury, Cheshire and is thought to have died in the same place in Cheshire. He was the husband of Elizabeth de Sandback and was the father of Maud Matilda de Radcliffe who connects to the Cometanic ancestry. Sir John was also the son of Sir John de Leigh II and Maud de Arderne. 

In Cometanic ancestry, Sir John is categorised as part of the 27th generation retrograde, and because he was born before 1453, he is classified as a medieval ancestor of Cometan, a title that is rarely bestowed.