Yusof bin Ishak DUT SK DUBC PJG (/ˈjʊsɒf bɪn ˈɪshɑːk/ YUUSS-off bin ISS-hahk; 12 August 1910 – 23 November 1970) was a Singaporean journalist and senior civil servant who served as the second Yang di-Pertuan Negara of Singapore from 1959 to 1965 and the first president of Singapore between 1965 and 1970, both roles serving as the head of state of Singapore. Born in the Federated Malay States, Yusof had his education in Malaysia and Singapore, graduating from Raffles Institution in 1929. Upon his graduation, he worked in journalism, creating a sports magazine with friends before joining Warta Malaya, a Malay-language daily newspaper. Leaving Warta in 1938, Yusof co-founded Utusan Melayu, a newspaper more centred on Malay issues, in 1939 with other Malay figures in Singapore.

Yusof held many appointments within the Singapore Government. He served on the Film Appeal Committee from 1948 to 1950 and was a member of both the Nature Reserves Committee and Malayanisation Commission for a year. In July 1959, he was appointed Chairman of the Public Service Commission. On 3 December 1959, Yusof succeeded Sir William Goode as Yang di-Pertuan Negara (English: Head of State) after the People's Action Party (PAP) won the 1959 general election. Yusof was subsequently appointed as the first president of Singapore by Parliament after the independence of Singapore on 9 August 1965.

Yusof served three terms in office (2 as Yang-di Pertuan Negara) before he died on 23 November 1970 due to heart failure. He was succeeded by Benjamin Sheares on 2 January 1971. Serving as Singapore's Head of State for close to 11 years between 1959 and 1970, he was Singapore's longest-serving Head of State until S. R. Nathan surpassed this record in August 2010. His portrait appears on the Singapore Portrait Series currency notes introduced in 1999.

Yusof was born on 12 August 1910 in Padang Gajah, a kampong village in Terong, Taiping, Perak, which was then apart of the Federated Malay States (present-day Malaysia). The eldest son of nine siblings, Yusof was of Malay and Sumatran descent. His father was of Minangkabau descent who lived in Penang before moving to Perak whilst his mother was of Malay descent who came from Langkat, North Sumatra.

His father was Ishak bin Ahmad, a civil servant who held the post of Acting Director of Fisheries. His younger brothers, Aziz Ishak and Abdul Rahim Ishak, were active in politics in Malaysia and Singapore respectively. Yusof received his early education at the Malay School and King Edward VII School, both in Taiping, Perak. In 1923, when his family moved to the Straits Settlements (present-day Singapore) after his father was posted there, Yusof studied at Victoria School. In 1924, he was enrolled in Raffles Institution for his secondary education.

During his time in Raffles Institution, he played various sports such as swimming, weight lifting, water-polo, boxing, hockey, baseball, and cricket. A member of the National Cadet Corps, Yusof became the first student to be made an officer, a Second Lieutenant. He was also apart of The Rafflesian, a school newspaper, and a prefect. In 1927, Yusof passed his Cambridge School Certificate examination and was awarded the Queen's Scholarship. With the scholarship, he studied at Raffles Institution for two more years, graduating in 1929. He was one of 13 students in the Queen's Scholarship class, along with being the only Malay student.

After graduating from Raffles Institution in 1929, Yusof began his career as a journalist and went into partnership with two other friends to publish, Sportsman, a sports magazine devoted entirely to sports. In 1932, Yusof joined Warta Malaya, a well-known newspaper during that time. Warta Malaya was heavily influenced by developments in the Middle East and Yusof wanted a newspaper dedicated to Malay issues. He fulfilled his vision by establishing Utusan Melayu with several Malay leaders in Singapore in May 1939.

During the Japanese Occupation of Singapore, Utusan Melayu had to stop circulation as machinery used to print the paper were requisitioned to publish the Japanese paper, Berita Malai. Yusof then moved back to Taiping and with the remaining money he had, he opened a provision shop and lived there until the war ended in 1945 and Utusan Melayu resumed publication. In 1957, Yusof moved to Kuala Lumpur and in February 1958, the headquarters of Utusan Melayu was also relocated to the city. During the post-war period, many Malays wanted independence of Malaya from the British and Yusof, fanned this fervour through his publications which resulted in the formation of the United Malay Nationalist Organisation (UMNO) in 1946. However, his democratic ideals were different from UMNO's vision of reestablishing the monarchy of Malaya. This resulted in rising tensions within the Utusan Melayu and in 1959, Yusof had sold his shares he had in the company and resigned as UMNO had bought over almost all of the shares of Utusan Melayu.

Yusof held several appointments within the Singaporean government, he had served on the Film Appeal Committee from 1948 to 1950 and was also a member of both the Nature Reserves Committee and Malayanisation Commission for a year. After his resignation from Utusan Melayu, Yusof took the position of Chairman of the Public Service Commission of Singapore at the invitation of then Prime Minister Lee Kuan Yew.

Following the People's Action Party's victory at the 1959 general elections, Yusof was appointed as Yang di-Pertuan Negara and was sworn on 3 December 1959, During his time as Yang di-Pertuan Negara, Singapore was divided by racial conflicts. Yusof actively promoted multiculturalism and reached out to people of all races to help restore trust and confidence after the 1964 racial riots.

On 9 August 1965, Singapore was expelled from Malaysia and became an independent nation. The position of Yang di-Pertuan Negara was abolished and Yusof then became the first President of Singapore. As president, Yusof reached out to the people to reassure citizens astonished by Singapore's expulsion and continued to promote multiculturalism and a national identity within the country by visiting constituencies and reached out to different racial and religious groups.

Yusof served for three terms in office before he died on 23 November 1970 due to heart failure.

Yusof is survived by his wife of 21 years, Puan Noor Aishah, and their three children, Orkid Kamariah, Imran, and Zuriana. Puan Noor Aishah continued her husband's legacy of public service and was the first Asian to become president of the Singapore Girl Guides Association. She and her now adult children were interviewed for the Channel NewsAsia documentary Daughters of Singapore, which screened in August 2015 as part of the SG50 celebrations and commemorated the spouses of Yusof Ishak and David Marshall, two pioneer leaders of Singapore.

Yusof participated in several sports in his youth. He won the Aw Boon Par Cup for boxing in 1932, and was the national lightweight champion in weightlifting in 1933. One of Yusof's hobbies was photography, and a collection of his photographs was donated to the National Archives of Singapore by his widow, Noor Aishah. He also cultivated orchids, and had the tennis courts at his residence on the Istana grounds, Sri Melati, converted into an orchid garden. He performed the pilgrimage to Mecca in 1963.

The following institutions bear Yusof Ishak's name:

• Yusof Ishak Secondary School, opened by then-Prime Minister Lee Kuan Yew on 29 July 1966.
• The Institute of Southeast Asian Studies (ISEAS) was officially renamed in August 2015 as the ISEAS–Yusof Ishak Institute on Yusof's 105th birthday, so its name will call to mind Yusof's "vision of equality, justice, harmony and strength amid diversity".
• Yusof Ishak House in National University of Singapore's Kent Ridge campus along Lower Kent Ridge Road.
• Masjid Yusof Ishak in Woodlands. The opening of this mosque in 2017 was officiated by the former president's widow, Puan Noor Aishah, and witnessed by guests including Prime Minister Lee Hsien Loong, Minister-in-charge of Muslim Affairs Yaacob Ibrahim, and Mufti Fatris Bakaram.

Other memorials include:

• The current series of Singapore dollar notes, the portrait series issued from 1999 onwards, features Yusof Ishak.
• In 2014, a wax figure of Yusof was unveiled at Madame Tussauds Singapore.
• For the celebration of Singapore's 50th anniversary of independence (SG50) in 2015, Yusof Ishak was featured in all set of six SG50 Commemorative Notes for which he champions the caused of meritocracy, multi-racialism and modernization of Singapore.
• Yusof is buried at Kranji State Cemetery, which is reserved for persons who have made a significant contribution to Singapore.

• Darjah Utama Temasek, 1st Class
• Sijil Kemuliaan, 1st Class
• Darjah Utama Bakti Cemerlang, 1st Class
• Pingat Jasa Gemilang, 1st Class
• Honorary Doctor of Letters, (National University of Singapore)

• Grand Commander of the Order of the Defender of the Realm (S.M.N., Tun) (Malaysia)
• Pingat Kemahkotaan 1961 (Selangor)
• Darjah Kerabat Laila Utama Yang Amat Dihormati (DK I, Dato Laila Utama) (Brunei), 1st Class
• Knight of the Order of St John (United Kingdom)

• Yusof Ishak Secondary School – a Secondary School in Singapore named in his honour.
• Masjid Yusof Ishak – a mosque located in Woodlands named in his honour.

Political offices
Preceded by Sir William Allmond Codrington Goode	Head of State of Singapore 1959–1970	Succeeded by Yeoh Ghim Seng
	Yang di-Pertuan Negara of Singapore 1959–1965	Position abolished Became President of Singapore
New office Previously Yang di-Pertuan Negara of Singapore	President of Singapore 1965–1970	Succeeded by Yeoh Ghim Seng