Muhammad Yasin bin Abdul Rahman (19 May 1922 – 18 July 2012), also known as Yassin Affandi, was a Bruneian politician who served as the president of the National Development Party from 2005 to 2010.

[4] During the occupation, the Japanese taught a number of Bruneian students, including Marsal Maun, Yassin, A. M. Azahari, Pengiran Muhammad Yusuf, and Jamil Al-Sufri.

He began work at British Malayan Petroleum Company (BMPC) in Seria at the end of 1947 as a storekeeper and advanced to senior local staff by the middle of 1948.

[4] Yassin was also involved at an early age in the Barisan Pemuda (BARIP) movement, which Sultan Ahmad Tajuddin supported.

At the time, the states of Sarawak and Sabah were included in the fight for Brunei's independence, and PRB was the only political party in Borneo.

[6] Yassin traveled to London in 1957, accompanied by the late Azahari and Zaini Ahmad, on behalf of PRB, to confer with the Colonial Office on the Brunei Constitution's draft.

[6] Assigned the task of coordinating the North Kalimantan National Army (TNKU) in August 1961 and participated in many closed-door talks in Jakarta with Indonesian legislators.

[6][10] On 12 July 1973, the day of Sultan Sir Omar All Saifuddin's birthday, Yassin and six other senior PRB detainees of the Berakas Detention Camp,[11] including Zaini, escaped by sea to nearby Limbang in Sarawak, thanks to an operation led by the nephew and brother of PRB leader Azahari, Sheikh Saleh Sheikh Mahmud.

The "springing" was reportedly given covert support by Ghazali Shafie, who served as the Minister of Foreign Affairs for the Malaysian government at the time.

[6] During the party's third convention in June 2008, he suggested that Brunei take over from Malaysia as the coordinator of the International Monitoring Team, which has been in charge of overseeing a provisional truce between the Government of the Philippines and the Moro Islamic Liberation Front (MILF).