Pierre Guérin de Montaigu (died 1230) was a nobleman from Auvergne, who became the 13th Grand Master of the Knights Hospitaller, in 1207–28.
He intervened in Armenia to help the Christian population against Suleiman of Iconium. He helped raise the siege of Acre by the Sultan of Damascus. He distinguished himself at the capture of Damietta during the Fifth Crusade, and subsequently toured European countries seeking support. On his return to Palestine, he found turmoil; he tried vainly to reconcile the Hospitallers with the Knights Templar. In 1228 he persuaded Pope Gregory IX to break the truce holding between Christian and Muslim powers. He refused to serve in the army commanded by Emperor Frederick II, who was excommunicated. He died in Palestine.