Sir John Dinham (1359–1428) was a knight from Devonshire, England. His principal seats were at Hartland in North Devon, Kingskerswell and Nutwell in South Devon, Buckland Dinham in Somerset and Cardinham in Cornwall. He killed one of the murderers of his father in Exeter Cathedral, for which he was pardoned by the king. He later broke into Hartland Abbey and assaulted the Abbot over a long-standing disagreement, and also performed other acts of violence. He married three times; his heir was John Dinham (1406–1458). His monument survives in Kingskerswell parish church.