John de Grauntsete or Grantsete (or John of Grantchester) (c. 1270 – c. 1350) was an English judge who lived in fourteenth-century Ireland. We know more about him than we do about any other contemporary Irish judge, and from the surviving information, we can form some idea of the lifestyle of an Irish judge in his time. He sat in turn in each of the Irish Courts of common law, and uniquely he is known to have appeared in Court as an advocate even after he became a judge.