The Free University of Brussels (French: Université Libre de Bruxelles) was a university in Brussels, Belgium established in 1834. The university, founded on the principle of secularism by Pierre-Théodore Verhaegen and Auguste Baron, formed part of a reaction to Catholic dominance in Belgian education. In 1969, during the Linguistic Wars, it split into two separate universities: the French-speaking Université Libre de Bruxelles (known as ULB) and the Dutch-speaking Vrije Universiteit Brussel (VUB).
The two universities continue to collaborate and are together referred to as the Brussels Free Universities.
In 1834, in response to the foundation of the Catholic University of Mechlin by the Catholic church, many recognized the need for a secular counterweight to the new Catholic university. After sufficient funding was collected among, including Freemasons, led by Pierre-Théodore Verhaegen and Auguste Baron, the Free University of Brussels was inaugurated on 20 November 1834, in the Gothic room of the city hall of Brussels. This day, called St V is still celebrated today. After its establishment, the Free University of Brussels faced difficult times, since it received no subsidies or grants from the government; yearly fundraising events and tuition fees provided the only financial means. Verhaegen, who became a professor and later head of the new university, gave it a mission statement which he summarized in a speech to King Leopold I: the principle of "free inquiry" and academic freedom uninfluenced by any political or religious authority.
The university's football team won the bronze medal at the 1900 Summer Olympics. After 1935 some courses were taught in both French and Dutch, but it was only in 1963 that all faculties held courses in both languages. During World War II, a resistance group, Groupe G, was formed among students at the university.