Juan Martín del Potro (Spanish pronunciation: [xwan maɾˈtin del ˈpotɾo]) born 23 September 1988) is an Argentinian professional tennis player. Del Potro's biggest achievement is winning the 2009 US Open singles title, where he defeated Rafael Nadal in the semifinals and the five-time defending champion Roger Federer in the final. He was the only man outside the Big Three (Novak Djokovic, Federer, and Nadal) to win a major between the 2005 Australian Open and the 2012 US Open, a span of 30 tournaments. Del Potro's other career highlights include reaching the 2018 US Open final, winning an Olympic bronze medal in singles at the 2012 London Olympics and the silver medal at the 2016 Rio Olympics, winning Indian Wells in 2018, and leading Argentina to the 2016 Davis Cup title. His career has been hampered by a succession of wrist and knee injuries.

Del Potro first entered the top 10 of the ATP rankings on 6 October 2008. In January 2010, he reached a then-career-high ranking of world No. 4, after which he withdrew from most of the season due to an injury to his right wrist. In 2016, del Potro led Argentina to its first ever Davis Cup title by defeating Croatia's Marin Čilić in the final from two sets down. He reached his first major semifinal in four years by defeating Federer in the quarterfinals of the 2017 US Open. In 2018, he won his first Masters 1000 title at the Indian Wells Masters, defeating the defending champion and world No. 1 Federer in the final. After reaching the semifinals of the 2018 French Open, he matched his career-high ranking of No. 4, and in August 2018 he reached the world No. 3 ranking for the first time. At the 2018 US Open, he reached his second major final, where he lost to Novak Djokovic. Del Potro did not play between June 2019 and February 2022 because of pain from a knee injury, and said he would retire as a result. During his career del Potro won 22 ATP singles titles and one doubles title.