Maksymilian Rafailovych Max Levchin (Ukrainian: ; born July 11, 1975) is a Ukrainian-American software engineer and businessman. In 1998, he co-founded the company that eventually became PayPal. Levchin made contributions to PayPal's anti-fraud efforts and was the co-creator of the Gausebeck-Levchin test, one of the first commercial implementations of a CAPTCHA challenge response human test. He founded or co-founded the companies Slide.com, HVF, and Affirm. He was an early investor in Yelp and was their largest shareholder in 2012. He left a leadership role in Yelp in 2015. Levchin was a producer for the movie Thank You for Smoking.