James Spencer Courier (born August 17, 1970) is an American former professional tennis player. He was ranked as the world No. 1 in men's singles by the Association of Tennis Professionals (ATP) for 58 weeks, including as the year-end No. 1 in 1992. Courier won 23 ATP Tour-level singles titles, including four majors – two at the French Open and two at the Australian Open – and is the youngest man in the Open Era to reach the final of all four singles majors, aged 22 years, 319 days. He also won five Masters titles and was part of the victorious United States Davis Cup teams in 1992 and 1995.

Since 2005, Courier has worked as a tennis commentator, notably for Nine (and previously Seven), the host broadcaster of the Australian Open. He is also an analyst for Tennis Channel and Prime Video Sport.

Courier was raised in Dade City, Florida, and though he excelled at youth sports in general, after a certain point it became clear that tennis was where his true talent lay. As a junior player in the 1980s, Courier attended the Nick Bollettieri Tennis Academy and won the prestigious Orange Bowl in 1986 and 1987 (the first to win back-to-back titles since Ivan Lendl), as well as the French Open junior doubles title in 1987.

Courier turned professional in 1988 and made his Grand Slam breakthrough at the 1991 French Open when he defeated Stefan Edberg and Michael Stich to reach his first Grand Slam final. In the final he defeated his former Bollettieri Academy roommate Andre Agassi in five sets to win his first Slam. "I didn't want to give him any easy points, and with that kind of wind anything could happen and anything did" Courier said afterwards. He made the quarterfinals of Wimbledon before losing to eventual champion Stich. At the US Open he defeated defending champion Pete Sampras in the quarterfinals and then Jimmy Connors in the semifinals, before losing the final to Edberg.

1992 saw Courier defeat Edberg in the final in four sets to win the Australian Open, and he celebrated by jumping into the nearby Yarra River. He then followed this result by defeating future Grand Slam champions Thomas Muster, Goran Ivanišević, Agassi and Petr Korda in the final in straight sets to successfully defend his French Open title. Afterward, Courier charmed the Parisian crowd by delivering a victory speech in French. Courier also enjoyed a 25-match winning streak during the season. In February of that year, following the San Francisco tournament, he became the tenth player to reach the world no. 1 ranking since the ranking system was implemented in 1973, and the first American since John McEnroe; he finished 1992 as the world no. 1 ranked player. Courier also was a member of the US team that won the 1992 Davis Cup. In 1992 he was the top-seeded player at the Olympics in Barcelona, where he lost in the third round to eventual gold medalist Marc Rosset from Switzerland.

In 1993, Courier again won the Australian Open, defeating Edberg in the final in four sets for the second consecutive year, and jumped into the Yarra a second time, but it was to be his last such celebration after contracting a stomach bug from the muddy and polluted river. He reached his third consecutive French Open final, which he lost to Sergi Bruguera in five sets. He also reached the 1993 Wimbledon final, defeating Edberg in the semifinals (Courier "used his attacking baseline game to keep Edberg off balance") and lost to Sampras in four sets. By reaching the Wimbledon final, Courier had reached the finals of all four Grand Slams at the age of 22, a record which still stands in men's singles. Courier also became the first player since Rod Laver to reach the finals of the Australian, French and Wimbledon in the same season; the feat was not matched until 2006 by Roger Federer. Courier again was part of the US team that won the 1995 Davis Cup.

Courier captured a total of 23 singles titles and 6 doubles titles during his career. He spent a total of 58 weeks ranked as the World No. 1 in 1992 and 1993. He reached the finals of all four major championships during his career, a feat accomplished by only seven other male players in the Open Era. Courier retired from the ATP tour in 2000. He was inducted into the International Tennis Hall of Fame in 2005.

Courier returned to the tour at the 2005 U.S. Men's Clay Court Championships when he received a wildcard into the doubles draw partnering Andre Agassi. The pair lost in the first round to eventual finalists Martín García and Luis Horna in three sets. It would be the last match of Courier's career.