Immigrants are critical to the U.S. artificial intelligence sector. To understand how immigration shapes AI entrepreneurship in the United States, we analyze the 2019 AI 50, Forbes’s list of the “most promising” U.S.-based AI startups. According to Forbes, these 50 companies had 125 founders in total. Using public data on their places of birth and educational histories, we estimate that 53 of these 125 founders (42 percent) were first-generation immigrants to the United States, and 33 of the AI 50 companies (66 percent) had at least one immigrant founder. An estimated 72 percent of these founders first came to the United States on student visas; the others came for professional opportunities, in many cases likely using H-1B work visas. These findings provide further evidence of immigrants’ importance within the U.S. AI ecosystem, and point to potential immigration reforms that could boost AI innovation and entrepreneurship in the United States.