Glebe Collegiate Institute (GCI) is a high school in the Glebe neighbourhood of Ottawa, Ontario, Canada. Administered by the Ottawa-Carleton District School Board (OCDSB), Glebe Collegiate Institute has approximately 1,700 students and is the district's largest school.

Students and sports teams are referred to as "Gryphons."

Glebe was selected as one of Canada's best schools in the August 23, 2004, edition of Maclean's news magazine.

The school offers specialized programs, such as French immersion, English as a second language, bilingual, gifted, and a learning disability and special education learning centre.

Glebe has a percussion group called Offbeat, which uses things like trash cans, brooms, chalk dusters, and water barrels as instruments. The school's Improv teams have twice placed within the Canadian Improv Games national finals. Glebe's robotics program participates in US FIRST international robotics competition, and won the SKILLS Canada STEM and Controls competition in 2015. They also have a student lead band called Ventana.

Glebe's Reach for the Top trivia team has won the national championships twice, during the 2020-2021 and 2021-2022 school years.

From 2012 through 2017, the Glebe Girls' Cross Country Team won 5 consecutive Overall OFSAA XC Titles, winning back to back Senior Girls titles in 2015 and 2016.

In 2008 and 2010, a group of four science teachers (Andrew Cumberland, Dan Lajoie, Colin Harris, and Masato Kachi) from Glebe placed second in Canada in the Discovery Channel's Iron Science Competition.