Undercover Billionaire is an American reality television series broadcast on the Discovery Channel.

The first season, which first aired from August 6 to September 24, 2019, followed billionaire Glenn Stearns as he attempted to start a million-dollar business in Erie, Pennsylvania, in 90 days, starting with $100, a car, and a tank of gas. Stearns identified his target business, gathered a crew to help, built his initial $100 stake sufficiently to fund a startup company, and opened a barbecue restaurant named Underdog BBQ. The presence of a Discovery Channel film crew was explained by saying that they were trailing him for a documentary about building a small business from scratch.

A TV special titled Undercover Billionaire: Return To Erie premiered on August 18, 2020.

The second season, which premiered on January 6, 2021, followed three self-styled successful entrepreneurs (Grant Cardone, Monique Idlett-Mosley, and Elaine Culotti) in three cities as they attempt to create a business with a "valuation of $1 million" in 90 days. Season 2 also featured part of Undercover Billionaire: Comeback City, a show about Stearns' continuing work in Erie, that debuted in its entirety on Discovery Plus.