Post-retirement
After his retirement as Prime Minister he continued to contribute to welfare organizations. He was instrumental in the setting up of the Tun Hussein Onn Eye Hospital. He was also an advisor to Petronas the country’s oil company and Chairman of Institute of Strategic and International Studies (ISIS).
During the 1987 UMNO leadership crisis, Tun Hussein fell out with Dr. Mahathir Mohamad, supporting Team B along with Tunku Abdul Rahman. Tun Hussein along with the Tunku, henceforth, became a strident critic of the Mahathir administration and died without having rejoined UMNO.
He died on the 29 May 1990 in Seaton Medical Center, San Francisco, at the age of 68. He had two sons and four daughters. He is buried in Makam Pahlawan (Heroes Mausoleum) near Masjid Negara, Kuala Lumpur.
Tun Hussein Onn was looked upon as being very sincere in his struggle for racial unity and had a reputation of being firm against anyone that tried to create racial unrest in the country and it was due to this, that he was known as Bapa Perpaduan or 'Father of Unity'.
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