Thomaz Koch (born May 11, 1945 in Porto Alegre), is a left-handed former tennis player from Brazil, who was a quarter-finalist at the French Open, Wimbledon and the U.S. National Championships.
He won at least 14 singles titles (3 in the Open era) and 3 Open era doubles titles. Whilst Koch's career-high ATP singles ranking was World No. 24 (achieved on December 20, 1974), he ranked inside the Top 20 in the 1960s before the invention of the ATP rankings, peaking at World No. 12.
He won two Gold medals in the men's tennis competition at the 1967 Pan American Games.