Walter de Islip, Isleep or de Istlep (died after 1348) was an English-born cleric, statesman, and judge in fourteenth-century Ireland. He was the first Chief Baron of the Irish Exchequer; he also held the offices of Treasurer of Ireland, Chief Escheator, and Custos Rotulorum of Kilkenny. He was a noted pluralist, who held numerous benefices. His career was seriously damaged by accusations of corruption and maladministration. He played an important role in the celebrated Kilkenny Witchcraft Trials of 1324.