Sekolah Menengah Sains Tuanku Jaafar (Tuanku Jaafar Science Secondary School; abbreviated STJ) is a fully residential schools (Sekolah Berasrama Penuh) in the state of Negeri Sembilan, Malaysia.

[2] The establishment aims was to provide science education to rural Bumiputera.

[3][4] Formerly known as Sekolah Menengah Sains Negeri Sembilan (SMSNS)[5], it was one of 10 SBP's on a trial basis in 1973 to comply with the aspirations of the New Economic Policy (NEP) as described in the Red Book of the Second Malaysia Plan 1971–1975.

[7] In 1994, the school was renamed to Sekolah Menengah Sains Tuanku Jaafar (SMSTJ).

The first group of students (The Pioneer) in 1973 stayed in the hostels and went to classes in King George V School, Seremban up to 1975 before moving to the current location in Kg.