In full, Ke Bawah Duli Yang Maha Mulia Al-Sultan Almu'tasimu Billahi Muhibbuddin Tuanku Alhaj Abdul Halim Mu'adzam Shah ibni Almarhum Sultan Badlishah (born November 28, 1927) was the fifth Yang DiPertuan Agong of Malaysia from September 21, 1970 to September 20, 1975 and twenty-eighth Sultan of Kedah since July 13, 1958.

Tuanku Abdul Halim (as he became), served as Deputy Yang DiPertuan Agong between September 21, 1965 and September 20, 1970.

The Yang DiPertuan Agong in a carriage with Queen Elizabeth II of the United Kingdom on a state visit to London, 1974.

The Yang DiPertuan Agong in a carriage with Queen Elizabeth II of the United Kingdom on a state visit to London, 1974.

He was elected as fifth Yang DiPertuan Agong of Malaysia and served his term in office from September 21, 1970 to September 20, 1975.

On November 2, 2006, Tuanku Abdul Halim was for the second time elected Deputy Yang DiPertuan Agong to serve a five-year term beginning December 13, 2006. He is the third person to have been elected twice to this office, after Tuanku Jaafar of Negeri Sembilan and Sultan Mizan Zainal Abidin of Terengganu.

Born at Istana Anak Bukit, Alor Star as Tunku Abdul Halim, he was the second, but eldest surviving son, of Tunku Badlishah (born 1894; reigned 1943-1958), who later became the 27th Sultan of Kedah. His mother was Tunku Sofiah binti Tunku Mahmud (b. 1910), who died in an automobile accident on February 28, 1935. Tunku Abdul Halim's maternal grandfather, Tunku Mahmud, was once Raja Muda or heir presumptive to the throne of Kedah.

He was educated at Alor Merah and Titi Gajah Malay schools and Sultan Abdul Hamid College in Alor Star between 1946 and 1948. He went on to Wadham College, Oxford and obtained a diploma in Social Science and Public Administration. He subsequently joined the Kedah Administrative Service, serving in the Alor Star district office and later, the state treasury.

On August 6, 1949 he was appointed Raja Muda or heir apparent and succeeded as twenty-eighth Sultan of Kedah on his father's death on July 13, 1958.He was installed at the Balai Besar in Alor Star on February 20, 1959.

Tuanku Abdul Halim presided over the first transfer of power of the civilian government when his uncle, Prime Minister Tunku Abdul Rahman resigned in favour of his deputy Tun Abdul Razak. Tunku Abdul Rahman had felt that he should not serve under a nephew, given strict Malay royal protocol, but agreed to stay on as prime minister for one day of Tuanku Abdul Halim's reign.

Tuanku Abdul Halim married twice:
In 1956 to Tuanku Bahiyah, daughter of Tuanku Abdul Rahman of Negeri Sembilan by whom he had three daughters. She served as Sultanah of Kedah and Raja Permaisuri Agong. She died on August 25, 2003 at Istana Kuala Cegar in Alor Star

In 1975 to Cik Haminah binti Hamidun, a commoner from Perak, who was titled Che Puan Kedah until January 9, 2004 when she was promoted to Sultanah.

Sultan Abdul Halim Airport in Kepala Batas, Alor Star, Tunku Abdul Hallim Road, Sultan Abdul Halim Building in Alor Star (Goverment Office), Sultan Abdul Halim Mosque in Kulim, Sultan Abdul Halim Bridge in Alor Star, Sultan Abdul Halim Highway and Sekolah Rendah Tunku Abdul Halim in Alor Star, the Sultan Abdul Halim Ferry Terminal in Penang, Sultan Abdul Halim Hospital in Sungai Petani and Sekolah Menengah Sultan Abdul Halim in Jitra, Kedah are all named after him.

He was the second youngest Yang DiPertuan Agong after Tuanku Syed Putra, beginning his reign at the age of 42 years 9 months 25 days.

If he is alive until December 2011, he may be the first person to be elected twice as Yang DiPertuan Agong.