King's College, Lagos (KCL) is a secondary school in Lagos, Lagos State, Nigeria. It was founded on 20 September 1909 with 10 students on its original site at Lagos Island, adjacent to Tafawa Balewa Square. The school admits only male students although historically some female HSC students were admitted before the establishment of Queen's College Lagos, popularly known as King's College's sister school. King's College conducts exams for the West African School-Leaving Certificate and the National Examinations Council.

Single-sex education, also known as single-gender education and gender-isolated education, is the practice of conducting education with male and female students attending separate classes, perhaps in separate buildings or schools. The practice of single-sex schooling was common before the 20th century, particularly in secondary and higher education.