Ong Keng Yong PPA PBS PJG (born 6 January 1954) is a Singaporean diplomat who served as the 11th secretary-general of ASEAN between 2003 and 2007.

Ambassador Ong Keng Yong is Executive Deputy Chairman of the S. Rajaratnam School of International Studies (RSIS) at the Nanyang Technological University in Singapore.

He is concurrently Director of the Institute of Defence and Strategic Studies (IDSS) and Head of the International Centre for Political Violence and Terrorism Research (ICPVTR) at RSIS.

Ong started his diplomatic career in 1979 and was posted to the Singapore Embassies in Saudi Arabia, Malaysia, and the United States of America between 1984 and 1994.

[3] In June 2024, Ong, discussing the 60th anniversary of ASEAN, continued to express optimism about its future, but stressed the need for collaboration in order to advance the prospects of its people.