A rthur Dantchik is an American billionaire trader and a co-founder of Susquehanna International Group (SIG), one of the world's largest and most successful quantitative trading firms. He founded the firm in 1987 with a group of friends, including fellow billionaires Jeff Yass and Gerald Segal. The founders met at the State University of New York at Binghamton and bonded over their shared passion for poker and statistical probability, which would become the philosophical foundation of their trading strategy.

SIG grew into a massive, privately held global trading giant, using sophisticated mathematical models to trade a wide variety of securities and derivatives. The firm is particularly known for its dominance in options market making. Dantchik has been a managing director and a key member of the executive committee since the firm's inception. Famously private, he and his partners have built a low-profile but immensely powerful financial firm. In recent years, a significant portion of their wealth has also come from a highly lucrative early investment in ByteDance, the Chinese parent company of the social media app TikTok.