Tuanku Al-Mutassimu Billahi Muhibbudin Sultan Abdul Halim Al-Muadzam Shah ibni Almarhum Sultan Badlishah (born 1924) in Alor Star, Kedah was the fifth Yang di-Pertuan Agong (roughly equivalent to King) of Malaysia from September 21, 1970 to September 20 1975, and Sultan of Kedah.

Born Tunku Abdul Halim, he was the second, but eldest surviving son, of Tunku Badlishah, then Raja Muda or Crown Prince of Kedah, by his consort Tunku Safiah binti Tunku Mahmud.

A graduate of Wadham College, Oxford, he succeeded his father in 1958. When elected Yang di-Pertuan Agong in 1970, he presided over the first ransfer of power in the civilian government when his uncle, Prime Minister Tunku Abdul Rahman Putra Al-Haj resigned in favour of his deputy Tun Abdul Razak. He returned as Sultan of Kedah on the 21st September 1975, and still reigns there.

Sultan Abdul Halim has had two official consorts:

1. Tuanku Hajjah Bahiyah, daughter of Tuanku Abdul Rahman ibni Almarhum Tuanku Muhammad of Negeri Sembilan, who died in 2004, and
2. Che Haminah Hamidun, a commoner from Perak, who is the current Sultanah of Kedah.