Selwyn House School (SHS) is an independent boys' school located in Westmount, Quebec. The school was founded in 1908 by Englishman Captain Algernon Lucas and was named in honour of Selwyn College at the University of Cambridge, which Lucas attended. Boys can attend from Kindergarten through Grade 11. The school body currently numbers 550 students with an average class size of 15 to 20 students.

Students are divided into four houses, which serve intramural athletics purposes within the primary school. The houses, named after the first four headmasters of the school, are Lucas (yellow), Macaulay (red), Wanstall (green) and Speirs (blue). The Selwyn House Gryphons have fielded strong athletic teams in recent decades and their traditional rivals in sports are Lower Canada College and Loyola High School. The school remains one of only three all-male educational institutions left in Quebec. They host co-ed events with sister schools Miss Edgar's and Miss Cramp's School and The Study.

Despite charging among the highest tuition fees for a private day school in Quebec, Selwyn House also previously took grants from the provincial government which is available to all private schools for Grade 7 to 11. All students in the secondary school section were therefore required to have a certificate of eligibility allowing them to attend government-funded English schools in Quebec. Prior to 2021, students without the certificate could only attend the non-subsidized primary section from Kindergarten to Grade 6, and must have received the required certificate by the end of Grade 6 in order to continue attending the school. Since 2021, Selwyn House no longer receives any government subsidies and students no longer need the certificate for any grade. By foregoing subsidies, the school is now able to broaden its potential student pool and admit the wealthiest students from French elementary schools who were previously barred from attending Selwyn House’s secondary school due to Bill 101.