Allan Glen's School was for most of its existence a selective fee-paying independent secondary school for boys in Glasgow, Scotland. It was founded by the Allan Glen's Endowment Scholarship Trust on the death in 1850 of Allan Glen, a successful Glasgow tradesman and businessman, "to give a good practical education and preparation for trades or businesses, to between forty to fifty boys, the sons of tradesmen or persons in the industrial classes of society". The School was formally established in 1853 and located in the Townhead district of the city, on land which Glen had owned on the corner of North Hanover Street and Cathedral Street.
Although notionally fee-paying, the school offered a large number of bursaries and enrolled pupils from all social classes, selected on the basis of academic ability. The school's emphasis on science and engineering led to it becoming, in effect, Glasgow's High School of Science. As such, in 1887 its management merged with the nearby Anderson's College to form the Glasgow and West of Scotland Technical College, which later became the Royal Technical College in 1912, the Royal College of Science and Technology in 1956, and ultimately the University of Strathclyde in 1964.
In 1912, the school was transferred from the new Royal Technical College to the School Board of Glasgow run by Glasgow Corporation. Parents who paid domestic or business rates to Glasgow Corporation were charged a much reduced fee, enabling children from less wealthy households but who had passed the entrance exam, to benefit from the high standard of teaching at the school. In 1923, playing fields were acquired for the school in the suburb of Bishopbriggs and in 1926 the school itself moved into the building previously occupied by Provanside Public School in North Montrose Street. In 1958 a new school building was planned on Cathedral Street, adjacent to the existing one. The new school building was opened in 1965.
Selective schooling was discontinued in local authority schools in 1972, and Allan Glen's merged with the City Public School to become a local co-educational comprehensive school on 22 August 1973, known as Allan Glen's Secondary School. Following a major re-organisation of school provision, brought about by falling birth rates, population migration and declining school rolls throughout the city, including Allan Glen's, the school was formally closed in 1989 and the buildings on Cathedral Street were converted into an annexe for the nearby Glasgow Central College of Commerce.
The playing fields first opened in Bishopbriggs in 1923 are still owned by the Allan Glen’s School Club and are the home ground of Allan Glen's RFC, who currently play in the West Regional League Division 1.
Although the school emphasised science and engineering, its former pupils are well-represented throughout the arts, sciences and engineering.