William Grimbaldeston (1571 – ????) was the 11th great-grandfather of Cometan, classified as one of Cometan’s distant maternal ancestors in the Prescott family line. Born in Kirkham, Lancashire, William was the son of Thomas Grimbaldeston and Margaret Whitehead and the father of John Grimbaldeston.
In Cometanic ancestry, William is classified as part of the 13th generation retrograde, thus categorising him as a distant ancestor of Cometan.