Sultan Yahya Petra Ibni Almarhum Sultan Ibrahim, GCMG, was the sixth Yang di-Pertuan Agong (King) of Malaysia from 21 September 1975 to his death, and twelfth (by some reckoning tenth) Sultan of modern Kelantan (1960-1979).
He was born Tengku Yahya Petra at Istana Balai Besar in Kota Bharu. He was the second son of Sultan Ibrahim ibni Almarhum Sultan Muhammad IV but the first by his commoner wife, Cik Embong binti Encik Daud, who was later promoted to the style Che Ampuan Besar by her son.
Sultan Yahya Petra (as he became) succeeded his father a day after the latter's death on 9 July 1960. He was crowned on 17 July 1961 at Istana Balai Besar in Kota Bharu. He served as Deputy Yang di-Pertuan Agong, the federal deputy king between 21 September 1970 until 20 September 1975.
During the election of the sixth Yang di-Pertuan Agong (the federal king), the most senior rulers Sultan Abu Bakar of Pahang and Sultan Ismail of Johor both declined to be considered. Sultan Yahya Petra also declined nomination at first due to having suffered a serious stroke, but changed his mind and was duly elected. His term began from 21 September 1975. Sultan Yahya Petra died in his sleep of an apparent heart attack at the National Palace on 29 March 1979.