In full, Sultan Haji Ahmad Shah Al-Mustain Billah ibni Almarhum Sultan Sir Abu Bakar Riayatuddin Al-Muadzam Shah (born October 24, 1930 at Istana Mangga Tunggal, Pekan) was the seventh Yang di-Pertuan Agong (roughly equivalent to King) of Malaysia from March 29, 1979 to April 25, 1984, and fifth Sultan of modern Pahang.

Born Tengku Ahmad Shah, he was the only son of Sultan Sir Abu Bakar Riayatuddin Al-Muadzam Shah ibni Almarhum Sultan Abdullah Al-Mutassimu Billah Shah (reigned 1932-1974) by his official and royal consort, Tengku Ampuan Besar Fatimah binti Almarhum Sultan Iskandar Kadasallah Shah.

A student of the Malay College Kuala Kangsar (MCKK), he received diplomas in public administration from Worcester College, Oxford and Exeter University. He succeeded his father as sultan in 1974.

His election as Yang di-Pertuan Agong in 1979 was marked with controversy as he was said to be at odds with the incoming prime minister Dr. Mahathir Mohamad. However, the rumours proved to be untrue and he proved to be a keen admirer of the prime minister.

Unlike other sultans, Sultan Ahmad Shah openly and loudly supports the Barisan Nasional government of Mahathir and his successor Abdullah Badawi. A controversial, headstrong personality, he has often forced his chief ministers to resign over minor differences. In 2003, he was accused by online newssite Malaysiakini.com of sexual assault on the Filipino nurse of his late wife, resulting in the birth of a daughter.

Sultan Ahmad Shah is a keen sportsman and President of the Malaysian Football Association (FAM).

His official and royal consort, Tengku Ampuan Afzan binti Tengku Panglima Perang Muhammad, a member of the Terengganu royal family, served as his Raja Permaisuri Agong but died of cancer on her return to Pahang on June 29, 1988. Sultan Ahmad Shah's junior wife, former Pakistani stewardess Kalsom binti Abdullah (nee Anita), was created Sultanah of Pahang in 1992.