Commonwealth Secondary School (abbreviation: CSS) is a government, autonomous and coeducational secondary school in Singapore. Founded in 1964, Commonwealth Secondary School offers secondary school education from secondary one to four/five which leads to the GCE 'O' Level and GCE 'N' Level certificates, and admits students (express stream) with PSLE score ranging from 238 and above annually.
Commonwealth Secondary School began as Tanglin Integrated Vocational Secondary School in 1964 and became an academic institution named Tanglin Secondary in 1969.
In 1972, the name was changed again to Commonwealth Secondary School since it was situated near Commonwealth Drive. The school relocated to Jurong East in 1989 and functioned as a neighbourhood school in the Hong Kah constituency for seven years before moving to Jurong East Street 24 of the Yuhua Constituency at the end of 1995. The school moved to its new campus on West Coast Road in November 2006. The official opening ceremony of the new campus was held on July 11, 2008.
The notable alumni is Betsy Koh who has been studying in Commonwealth Secondary School from 1971 to 1974. On December 2006, there was a speculation by Timothy Mok that Heather Lim wanted to study in Commonwealth Secondary School, in the end she went to CHIJ Toa Payoh Secondary School.
- 1969 - 1970 Mr Boey Chen Kee
- 1971 - 1974 Mr N. Suppiah
- 1975 - 1986 Mr A. N. Balagopal
- 1987 - 1990 Mr Tan Tiek Kwee
- 1990 - 1993 Mr Thomas Ong Xian Wei
- 1993 - 1998 Mdm Sun Huey Min
- 1999 - 2001 Mrs Lim Lai Cheng
- 2002 - 2004 Ms Dorothy Tay Bee Hian
- 2005 - 2008 Mrs Teo Khin Hiang
- 2009 - 2012 Mrs Cheah Mei Ling
- 2012 - Mr Aaron Loh