Lim Siong Guan is Chairman of the Singapore Economic Development Board. He spearheaded the PS21 movement in the Singapore Public Service, to transform the service for the 21st century and re-orientate it for excellence in the delivery of government policy. He drives the e-government efforts, and chairs a Public Service Committee tasked to cut bureaucracy, promote economy, pursue organisational excellence and harness Information Technology in the public sector. Siong Guan was the Head of the Singapore Civil Service until 31 March 2005. He held the post of Permanent Secretary in the Ministry of Finance, the Prime Minister's Office, the Ministry of Education and the Ministry of Defence.

He was Chairman of the Accounting and Corporate Regulatory, the Inland Revenue Authority of Singapore and the Central Provident Fund Board. He also sat on the board of the Monetary Authority of Singapore, Institute of Policy Studies and the Institute of Southeast Asian Studies. He has been a Director of DBS Bank Ltd, a Director of Neptune Orient Lines Ltd, and variously Chairman or Director of a number of companies which are now part of the Singapore Technologies Engineering group of companies.