Chung Hyeon

2019 saw him struggle with injury, falling outside of the top 150 from a career-high ranking of 19. Chung returned at 2019 Chengdu Challenger.

At Indian Wells, Chung beat Dušan Lajović, Tomas Berdych and Pablo Cuevas to advance to his maiden Masters quarterfinals appearance, but lost to Roger Federer in straight sets. At Miami, Chung defeated Matthew Ebden, Michael Mmoh, and João Sousa, reaching the quarterfinals where he lost in straight sets to John Isner, who went on to win the tournament. He did not compete at the 2018 French Open or 2018 Wimbledon Championships.

Chung scored his first Australian Open match by defeating Renzo Olivo. He lost in the second round against eventual semifinalist Grigor Dimitrov despite winning the first set. In April, Chung reached the quarterfinals of the 2017 Barcelona Open Banco Sabadell, taking Rafael Nadal to a tie-break before eventually losing. To reach the quarterfinals, Chung came through qualifying and the main draw to record six wins in a row without dropping a set, including victories over Denis Istomin, Phillip Kohlschreiber and Alexander Zverev.

In May, Chung competed at the 2017 BMW Open in Munich, reaching the semifinals. In the second round, Chung recorded a victory against Gael Monfils, who at a ranking of No. 16 was the highest-ranked player Chung had defeated. At the French Open, Chung achieved his first Grand Slam breakthrough by reaching the third round, including a win over 27th seed Sam Querrey in the first round. He lost against the eighth seed Kei Nishikori in five sets.

After the 2016 French Open, Chung took nearly four months off to recover from an abdominal injury.

Chung reached the final qualifying round for the Australian Open, but focused his efforts on the Challenger Tour. He won at the Burnie Challenger in February to reach the world's top 150 and subsequently received a Wildcard for the ATP World Tour competition at the Miami Open, getting to the second round of this Masters level tournament. Two further Challenger titles followed in April and May 2015, which saw him enter the world top 100 for the first time. His rapid rise up the rankings and an error on behalf of the Korean Tennis Federation meant that he missed the entry deadline for the 2015 French Open. Although he was later handed a wildcard into the qualifying tournament, he was eliminated in the first round. Chung then lost in straight sets to unranked Nicholas Monroe in the first round of qualifiers in the Topshelf Open. In the 2015 Wimbledon Championships, he reached his first main draw in a Grand Slam tournament, losing in five sets in the first round to Pierre-Hugues Herbert. Immediately following his first round loss at Wimbledon, Chung returned to his home country and won the Men's Singles and Men's Team events at the 2015 Summer Universiade in Gwangju. At the 2015 US Open, Chung qualified for the main draw and recorded his first win in a Grand Slam against James Duckworth. Chung lost in the second round against fifth seed Stanislas Wawrinka in straight sets, despite taking each set to a tiebreak. He continued to play on both the Challenger and ATP tour through 2015, winning a further Challenger at Kaohsiung in September and reaching his first ATP quarterfinal at the Shenzhen Open. He was awarded the year-end ATP Most Improved Player award for 2015, after climbing over 120 places to No. 51 in the rankings.

2014 saw Chung move full-time to the men's professional game, winning three Futures tournaments and the 2014 Bangkok Open, his first Challenger level tournament. He competed in the qualifying for the 2014 US Open and won two matches for the South Korea Davis Cup team to help keep them in the Asia/Oceania Zone Group I. He also won gold in the doubles competition at the 2014 Asian Games and ended 2014 ranked 151 in the ATP Rankings.

In February, Chung lost in Sofia in the first round to qualifier Marius Copil. In Rotterdam Chung reached second round, where he lost to Viktor Troicki. In Marseille he lost in the first round to David Goffin. In Dubai Chung defeated Andreas Seppi in the first round. Then he lost to Roberto Bautista Agut, winning only a single game in this match. Chung won both singles in the Davis Cup tie against New Zealand. South Korea won 3–1.

Chung won his first round match in Brisbane against Sam Groth. He lost in the second round to the 3rd seed Marin Čilić. At the Australian Open Chung lost in the first round to Novak Djokovic.

Chung took up tennis as a way to try to help maintain his eyesight after requiring glasses at a young age. He won the Eddie Herr International and Junior Orange Bowl Boys under-12s titles in December 2008, and was subsequently signed, along with his brother Chung Hong, to the Nick Bollettieri Tennis Academy at IMG in Florida. He began competing on the ITF junior tour in 2012, and was runner-up in the 2013 Wimbledon Boys' Singles, a month after winning his first Futures title. He later competed in his first ATP tournament, the Malaysian Open, being defeated in the first round. He reached a career junior high of No. 7, with an 84–32 win-loss record.

At the Australian Open, Chung made his breakthrough into the limelight by becoming the first South Korean player, male or female, to advance past the fourth round of a Grand Slam tournament. In the third round, he achieved his first victory over a Top 10 player, defeating world No. 4 Alexander Zverev in five sets. In the next round, Chung won a straight sets match against six-time Australian Open champion and former world number one Novak Djokovic, who had just returned from injury. This marked the first time since 2007 that Djokovic had lost in straight sets at the Australian Open. In the quarterfinals, Chung defeated unseeded American Tennys Sandgren to reach his first Grand Slam semifinal. He became the youngest Australian Open semifinalist since Marin Čilić in 2010 and the lowest ranked since then-No. 86 Marat Safin in 2004. Chung played Roger Federer in the semi-final, but withdrew due to foot blisters when he was close to going two sets down. The Korean also played the doubles event with Radu Albot and defeated the defending champions Henri Kontinen and John Peers.

Chung Hyeon (Korean: 정현 ; Hanja: 鄭泫 ; Korean pronunciation: [tɕəːŋ çʌn] ; born 19 May 1996) is a South Korean professional tennis player. He is currently the second highest ranked South Korean and also the 2017 Next Gen Finals champion. As an unseeded player, he became the first Korean player to reach a Grand Slam semifinal at the 2018 Australian Open.

Seeded 24th at the Australian Open, Chung faced Bradley Klahn in the first round. He narrowly lost the first two sets in tiebreakers, but came back to win in five sets, advancing to the second round where he lost in four sets to Pierre-Hugues Herbert.