Richard Spencer's University of Florida event was denied this week after the school ruled against having the white nationalist's group on campus in September.
Spencer's supporters have vowed to file a court challenge.
UF President W. Kent Fuchs said in a statement that the decision was made after assessing risks to the campus, community, and law enforcement following last weekend's deadly violence during a white nationalist rally in Charlottesville, Virginia.
Members of the National Policy Institute, which is headed by Spencer, had contacted the university about renting space on the campus in Gainesville on Sept. 12.
"I find the racist rhetoric of Richard Spencer and white nationalism repugnant and counter to everything the university and this nation stands for," Fuchs' statement said.
Fuchs said UF is dedicated to free speech and public discourse, but the First Amendment does not require risk of imminent violence to students.
Spencer did not return a text seeking comment.
But Cameron Padgett, a Georgia resident affiliated with Spencer's group who was coordinating the campus event in Gainesville, told The Associated Press he would be filing a legal challenge.
"I signed an agreement and sent it in to the event coordinator," Padgett said. "I don't know who's advising them on why they think they can do this."
Padgett filed a challenge after Auburn University tried to ban Spencer's appearance there in April. A federal judge ruled against Auburn, and the talk was held as planned. The university was also ordered to pay nearly $30,000 in legal fees.
Several hundred people attended the event and three people were arrested outside the building during clashes between Spencer's supporters and his opponents.
Janine Sikes, a UF spokeswoman, said this is the first time that officials can recall the university denying such a request due to fears of violence or hate speech.
"I can't say for the last 100 years, but we're not aware of ever doing this in recent history."
The move comes after Texas A&M University canceled a planned September white nationalist protest on its campus featuring Spencer, due to security concerns.
Spencer, a leading figure in the white nationalist movement, has popularized the term "alt-right" to describe a fringe movement that is a mix of white nationalist, white supremacist, anti-Semitic and anti-immigration beliefs. Spencer has advocated for an "ethno-state" that would be a "safe space" for white people.
After Donald Trump was elected president, Spencer hosted a conference in Washington that ended with audience members mimicking Nazi salutes after Spencer shouted, "Hail Trump, hail our people, hail victory!"