Hussein bin Onn (Jawi: حسين بن عون; 12 February 1922 – 29 May 1990) was a Malaysian lawyer and politician who served as the third prime minister of Malaysia from 1976 to 1981.

Hussein Onn was born on 12 February 1922 in Johor Bahru to an aristocratic family. His father, Onn Jaafar (1895–1962) was a pioneer of early Malay nationalism and helped found the United Malays National Organisation (UMNO), serving as its inaugural president. His mother was Halimah Hussein (1900–1988). Hussein's grandfather, Jaafar Haji Muhammad, was the first Menteri Besar of Johor, or Chief Minister, while his grandmother, Rogayah Hanim, is generally understood to have come from the Caucasus region of the Ottoman Empire. She was likely presented as a concubine (see Circassian beauties) by the Ottoman court to the Sultan of Johor, but her exact origins are unclear. Through Rogayah, Hussein is also cousin to academics Ungku Abdul Aziz, Syed Hussein Alatas, and Syed Muhammad Naquib al-Attas.

In 1948, Hussein married Suhailah Noah, a daughter of first Speaker of the Dewan Rakyat Mohamed Noah Omar. Abdul Razak Hussein was his brother-in-law by virtue of his marriage to another of Mohamed Noah's daughters, Rahah Noah.

Hussein received his early education at Telok Kurau Primary School, Singapore, and at English College Johore Bahru. Hussein's Grade 2 result in his Senior Cambridge exams rendered him ineligible for either Raffles College or the King Edward VII College of Medicine, which combined with the outbreak of World War II, led him to join the Johor Military Forces as a cadet in 1940. A year later, he was sent to the Indian Military Academy in Dehradun, India. By the completion of his training, what was meant to be a two-year ordeal condensed into eight months, Malaya had been occupied by Japan and Hussein was commissioned into the 19th Hyderabad Regiment of the British Indian Army as a second lieutenant. Initially assigned to train new recruits in Agra, Hussein was later sent to the Middle Eastern theatre.

In early 1943, Hussein was called to New Delhi to serve as part of the military intelligence department of the British Military Headquarters in preparation for the British invasion of Malaya. He was later posted to Rawalpindi as an instructor at the Malayan Police Recruiting and Training Centre, where he instructed a police force that would enforce order upon British re-occupation. Hussein was part of the second wave of an invasion force heading towards Malaya when the Japanese surrendered, whereupon he was diverted to Yangon before arriving in Singapore in 1945.

Following his return, Hussein was appointed the Commandant of the Johor Bahru Police Depot under the British Military Administration, where he was responsible for re-establishing a police force. When the military administration was replaced by civilian rule the following year, Hussein opted to leave the army when it refused to grant Malay officers equal status to their British counterparts. He instead joined the Malay Administrative Service, becoming the assistant district officer for Kuala Selangor and later Klang. He left the service in 1949, opting to commit to politics.

Hussein went to London to study law at Lincoln's Inn in 1952. He passed his exams in 1960 and was called to the Bar in 1961.

When Hussein's father Onn founded UMNO in 1946, he joined it as the head of its youth committee. He was later elected the party's first youth chief in 1949. In 1950, he was elected UMNO secretary general. The same year, he was appointed to the Federal Legislative Council, serving on its Integrity Services Commission responsible for investigation allegations of corruption against British officials. He was concurrently a member of Johor's legislature and executive council.