The Guelph Collegiate Vocational Institute (GCVI, Guelph C.V.I., GC) is a public high school in Guelph, Ontario, Canada. The school is the oldest continuously operating public high school in Guelph, and the third oldest in the province of Ontario, Canada.

The Guelph Collegiate Vocational Institute consists of four main buildings. The Old Building (building A) consists of three levels. The bottom level holds the visual arts department, chemistry department and a general sciences department. The floor above holds the guidance department, main office, geography department, math department and an auditorium that extends up into the top floor. The top floor holds the English department, family studies department and the biology department.

Building B (the New Building) has three levels as well. The business and economics departments, as well as the physics department and the nurse's office, are located on the lowest floor. A computer education department is located on the second level. The history and current languages departments are on the upper floor. Building C is divided into two floors. Three distinct gymnasiums are located on the first floor. The cafeteria of the school is above. The school's technology and music departments are housed in Building D. There are nine separate shops in the technological sector. They include: integrated technology, transportation technology, manufacturing technology, construction technology, communication technology, technological design, computer engineering technology and computer information science.

The Old Building of the Guelph Collegiate Vocational Institute consists of building styles that are unique only to that school in the City of Guelph. The original oak doors are still present from the building's original construction in 1923. Marble and granite encase all of the hallway floors throughout The Old Building. The hallways on the main floor of The Old Building measure an outstanding 18 ft. in height. The main entrance way into the school is surrounded by a large archway. It is easy to see the vast number of students who have walked the halls of G.C.V.I. as there are large indents that have been left in the granite stairways of the school from many thousands of feet walking up and down them each day.

This article's list of alumni may not follow Wikipedia's verifiability policy. Please improve this article by removing names that do not have independent reliable sources showing they merit inclusion in this article AND are alumni, or by incorporating the relevant publications into the body of the article through appropriate citations. (December 2017)

• Mike DeAngelis, guitarist, the Arkells
• Arthur William Cutten
• George Alexander Drew
• Charley Fox
• Beth Goobie
• Hugh Guthrie, K.C.,M.P.
• Alfred Dryden Hales
• William Ernest Hamilton
• James Jerome Hill
• Harry Howell, played for the Guelph Biltmore Mad Hatters
• Edward Johnson
• Ted Jolliffe, Ontario CCF Leader
• Luke Kirby
• Jean Little
• John Kenneth Macalister
• Andrew P. MacDonald
• John McCrae, famous WWI physician and author of In Flanders Fields
• Kelly Richardson
• Joey Slinger
• Virginia to Vegas, stage name of Derik Baker
• Liz Sandals
• Donna Strickland, recipient of the Nobel Prize in Physics in 2018 and professor at the University of Waterloo
• Tavius Robinson, NFL Linebacker for the Baltimore Ravens

• Former Prime Minister John Diefenbaker married a GCVI teacher, and made two prominent visits to the school including a stop as opposition leader in 1957, just weeks before being sworn in as Prime Minister, and one as Prime Minister in 1963 just before losing the next election to Liberal Leader Lester B. Pearson
• John Diefenbaker's first visit launched the 17-year political career of Alfred Dryden Hales, alumnus of G.C.V.I. Hales chaired the Public Accounts Committee for 6 years, and was beloved by his constituents.
• Less than 24 hours before Diefenbaker's first visit Prime Minister Louis St. Laurent stopped at the school. Diefenbaker drew a much larger and much more enthusiastic crowd (a sure sign of what was to come in the election).
• John Diefenbaker had replaced George Alexander Drew (a former GCVI Student) as leader of the Conservative Party less than a year before becoming Prime Minister in 1957.
• During the Ontario provincial elections of 1943, 1945 and 1948, both the Premier George Alexander Drew and Opposition Leader Edward Bigelow (Ted) Jolliffe were former GCVI Students, so regardless of who won the election the Premier of Ontario would have been a GCVI alumnus.
• George Alexander Drew was the second GCVI student to hold the position of Federal Leader of the Opposition, following Hugh Guthrie, who held the post for little under a year in the early half of the 20th century.

• Education in Ontario
• List of secondary schools in Ontario

Philip Clendenning. Soviet Observer. A Memoir of my very small Part in the Collapse of the Soviet Union (Newtonville, MA 2012). Long chapter on student life at GCVI, 1955–1960.

• http://www.ugdsb.ca/gcvi/ - Main Page
• http://www.gcviactanostra.com Archived 2007-10-09 at the Wayback Machine - GCVI Yearbook