Gaykhatu (Mongolian: Gaikhalt; Mongolian Cyrillic: Гайхалт, died 1295) was the fifth Ilkhanate ruler in Iran. He reigned from 1291 to 1295. During his reign, Gaykhatu was a noted dissolute who was addicted to wine, women, and sodomy, according to Mirkhond. His Buddhist baghshi gave him the Tibetan name Rinchindorj.
His name means "amazing/surprising" in the Mongolian language as in "gaikhakh" (to get surprised).
He had originally been governor of Seljuk Anatolia, and was nominated for the throne by an influential Mongol commander, Ta'achar, who had murdered Gaykhatu's brother, the then paralyzed Ilkhan Arghun. Ta'achar intended to promote Baydu, but when Baydu didn't appear at the quriltai, Gaykhatu was enthroned instead. During his reign, the princess Kökötchin had arrived from the court of his Khagan Kublai, escorted by none other than Marco Polo. The new Ilkhan decreed that the princess be married to his nephew Ghazan, who had fully supported his right to rule. Gaykhatu's wife, Padshah, was the daughter of Kütlugh Turkan (Turkan Khatun) of Kirman. Padshah had taken the title of Safwat al-dunya wa al-Din (literally, Purity of the earthly world and of the faith) after Djalal da-Din Abu'l-Muzzafar was deposed as head of the Mongol tribe that reigned in southeastern Iran. Padshah was known for the murder of her stepbrother, Suyurghatamish. One of his clansmen, Khurdudjin, managed to avenge him by putting her to death, with the tacit approval of the later Ilkhan, Baydu.