Thomas Muster (German: [ˈmʊstɐ]; born 2 October 1967) is an Austrian former professional tennis player. He was ranked as the world No. 1 in men's singles by the Association of Tennis Professionals (ATP). Muster won 44 ATP Tour-level singles titles, including the 1995 French Open and eight Masters titles. One of the world's leading clay court players in the 1990s, at his peak he was called "The King of Clay". He is the first Austrian to win a major singles title, followed by Dominic Thiem at the 2020 US Open.
Muster first came to prominence when he reached the final of the French Open junior tournament and the Orange Bowl juniors tournament in 1985.
Muster played his first matches at the top-level in 1984, as a junior player, at the age of 16. In 1984, he played his first match for Austria in the Davis Cup. He also played at the 1984 Summer Olympics in Los Angeles, and in two tournaments on Austrian soil, the clay-court event in Kitzbühel and the indoor carpet event in Vienna.
Muster turned professional in 1985, regularly playing in Challenger tournaments throughout the year, winning in Belo Horizonte, as well as continuing to play in many top-level tournaments. Muster won his first top-level tournament at the Dutch Open in Hilversum in 1986.
In 1988, Muster reached six top-level tournament finals, winning four of them, in Boston, Bordeaux, Prague and Bari. Muster finished the year ranked 16th in the world.
Early in 1989, Muster became the first Austrian to reach the semifinals of the Australian Open, eventually losing in four sets to world No. 1, Ivan Lendl on a very hot day. Shortly after that, he became the first Austrian to reach the world top 10. On the night of 31 March 1989, he defeated Yannick Noah in five sets in the semifinals of the Lipton International Players Championships in Key Biscayne, Florida, to set up a final against Lendl. However, in the early hours of 1 April 1989, just hours after his semifinal victory, he was struck by a drunk driver, severing ligaments in his left knee and forcing him to default the final. Muster flew back to Vienna to undergo surgery. With the aid of a special chair designed to allow him to practice hitting balls while recovering from knee surgery, he returned to competitive tennis in September 1989.
Muster's comeback continued in 1990, when he won three top-level tournaments on clay (including the Italian Open, defeating Andrés Gómez in the semifinals and Andrei Chesnokov in the final) and one title on hardcourt. Muster reached the semifinals of the 1990 French Open, losing in straight sets to the eventual champion, Andrés Gómez. He also helped Austria reach the semifinals of the Davis Cup, where they were eliminated 3–2 by the United States, despite winning both of his singles rubbers against Michael Chang and Andre Agassi. That year, he was named the ATP Tour's "Comeback Player of the Year."
In 1990, Muster won the Austrian Sportsman of the Year award. He won two more top-level tournaments in 1991, and three more in 1992 (all on clay courts), with the biggest of these titles being the 1992 Monte Carlo title, where he defeated Aaron Krickstein in the final. In 1993, Muster won seven titles. Muster's win–loss record on clay in 1993 was 55–10, although he failed to win any of the four big clay-court events of the year.
At both the 1992 and 1993 French Opens, Muster was defeated by the reigning French Open and Australian Open champion Jim Courier. At the 1994 French Open, he won his second round match against Andre Agassi in five sets but was then defeated by the serve-and-volley play of Patrick Rafter in the next round, with Rafter's four set victory denying Muster a match against the reigning French Open champion Sergi Bruguera.
Muster won three clay-court titles in 1994. In March 1994, he defeated Michael Stich of Germany in a first round Davis Cup tie in Graz, 6–4, 6–7, 4–6, 6–3, 12–10, after saving a match point when trailing at 7–8 in the fifth set. Despite Muster's win over Stich bringing Austria level at 2–2 in the tie, it was Germany who eventually won the decisive fifth rubber.
In 1995, Muster enjoyed the best year of his career winning 12 tournaments, with 11 of those tournaments won on clay-courts. Between February and June 1995, Muster won 40 consecutive matches on clay (the longest winning streak on the surface since Björn Borg had won 46 matches between 1977 and 1979). At the 1995 Monte Carlo Masters, he defeated Andrea Gaudenzi in the semifinals, despite struggling heavily in the latter stages of the match due to having a shortage of glucose in his blood and suffering a 40° fever, which required a brief spell in hospital after the match. The next day, he won the final against Boris Becker, in five sets, with Muster surviving two championship points in the fourth set tiebreak, the first of which saw Becker double-faulting after going for a big second serve. He went on to win his second Italian Open title, defeating Sergi Bruguera in the final. At the 1995 French Open, Muster won his first and only Grand Slam singles title, defeating Yevgeny Kafelnikov in the semifinals and comfortably beating 1989 champion Michael Chang in the final in straight sets. Muster was the only Austrian to win a Grand Slam singles title until Dominic Thiem won the 2020 US Open. His win–loss record on clay in 1995 was a remarkable 65–2. Although his record on other surfaces was less impressive, a late season victory over Pete Sampras on fast indoor carpet during his run to the title of the 1995 Eurocard Open (October) – Singles Masters event in Essen, Germany, gave Muster an outside chance at finishing the year no. 1; however, Sampras finished the year at no. 1. Of the 12 tournaments that Muster won in 1995, he saved at least one match point held against him during six of them, with those six tournaments being held in Estoril, Barcelona, Monte Carlo, St. Pölten, Stuttgart Outdoor and Umag.
In 1995, Muster won the Austrian Sportsman of the Year award for the second time. He continued to rack up clay-court victories in 1996. He won seven tournaments, six of them titles he successfully defended after winning them the year before. These 1996 tournament victories included his third Monte Carlo title, where he defeated clay court specialist Albert Costa in the final, and his third Italian Open title, defeating Richard Krajicek in the final. Muster's win–loss record on clay in 1996 was an impressive 46–3. This made his 1995–96 record on the surface 111–5, which was, at the time, the best two-year clay-court record since the open era began in 1968. Despite Muster's continued dominance on clay-courts in 1996, he was upset in the Round of 16 at the 1996 French Open, losing to eventual finalist Michael Stich in four sets. In July 1996, in the final of the 1996 Mercedes Cup in Stuttgart, Muster defeated newly crowned French Open champion Yevgeny Kafelnikov in three straight sets.
In February 1996, Muster attained the world no. 1 ranking for the first time. He held the ranking initially for just one week, and then regained it for five weeks over March and April 1996. The validity of Muster's number one ranking was called into question by top Americans Pete Sampras and Andre Agassi, who argued that he had achieved the top spot based almost solely on his clay court results, although Muster had beaten Sampras on indoor carpet at the 1995 Masters event in Essen, Germany, and Agassi had only won tournaments on hardcourt in 1995.
In 1997, Muster enjoyed the best results of his career on hardcourt. He reached the semifinals of the 1997 Australian Open, losing to eventual champion Pete Sampras. He then went on to win the tournament in Dubai, defeating Goran Ivanišević in the final. Following a semifinal showing at the 1997 Newsweek Champions Cup and the State Farm Evert Cup in Indian Wells, California, Muster won his biggest title on hardcourt at the 1997 Miami Masters, the same tournament where his career had nearly ended eight years earlier. After a semifinal victory over Jim Courier—his third successive win over the American in early 1997—Muster defeated Sergi Bruguera in three straight sets in the final. Bruguera had defeated Sampras in the semifinals.