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He's made a name for himself by building a company with an estimated $50 billion valuation.
He's also said some things that have gotten him into hot water. In the past, he's referred to the competition as "an as-hole named Taxi."
It doesn't help that Uber reportedly launched a campaign called Operation SLOG, an aggressive plan to poach Lyft drivers, last year.
Kalanick addressed his reputation at an event celebrating Uber's five-year anniversary since its launch: "I realize that I can come off as a somewhat fierce advocate for Uber," he said. "I also realize that some have used a different 'a'-word to describe me."
Uber has seen crazy growth in the past year - now, the company operates in more than 300 cities in 58 countries. But Uber also had some public relations blunders in the past year. At a dinner for influencers, an Uber executive threatened a smear campaign against a journalist and later used its "God View" tool to track another.
At Uber's fifth anniversary event, Kalanick went on to say: "Well, I'll be the first to admit that I'm not perfect, and neither is this company. Like everyone else, we make mistakes, but at Uber we are passionate about learning from them. And the reason I'm so proud of what we've already done - the reason I believe so strongly in what we're trying to do - is because in city after city, we've seen it work."
And then there was more troubling privacy news: An Uber interview candidate in Washington, D.C. was reportedly given access to Uber's rider database, which is full of sensitive information, for hours after his interview was over, The Washington Post reported. While researching a story about the company, San Francisco magazine editor Ellen Cushing was allegedly warned by Uber employees that Uber might look at her rider logs, too.
Concerns about privacy don't seem to be hurting the company, however. The company has 3,000 employees around the world, and its millionth driver just gave his or her first Uber ride, Kalanick announced. Uber now has more than 1 million square feet of office space globally.
You can watch Kalanick's whole speech here: