The pop singer made the announcement on Instagram Sunday (Nov. 4), just two days before the upcoming midterm elections on Tuesday.
RiRi wrote that Floridians "have the opportunity to make history this election" by electing Gillum as the first African-American governor of Florida.
"If you’re tired of feeling like you don’t matter in the political process, know the most important thing you can do in supporting a candidate is finding someone who will take on critical issues," she captioned a black-and-white image of a woman holding a sign that reads "Grab Em By the Midterms."
The singer's post also called for the repeal of the state's controversial "stand your ground" law, which allows Florida residents to defend themselves with deadly force if they are in fear of imminent danger or death, according to NBC News.
Rihanna concluded the post by encouraging Floridians to vote yes on Amendment 4, which restores voting rights to people who have been convicted of a felony and have completed the terms of their sentence.