The 1999 Australian Open was a tennis tournament played on outdoor hard courts at Melbourne Park in Melbourne, Australia. It was the 87th edition of the Australian Open and was held from 18 through 31 January 1999. This was the first Grand Slam of the calendar year. Total attendance for the event reached 391,504.

In the singles competition, Petr Korda and Martina Hingis were the defending champions. Korda was unseeded at this tournament and was eliminated in the third round by American 15th seed Todd Martin. This loss resulted in him falling down the rankings from 20th to 76th. Later in July, Korda received a suspension from tennis by the ITF after testing positive for nandrolone at Wimbledon last year. Yevgeny Kafelnikov, on the other hand, ended up becoming the men's champion, defeating surprise finalist Swede Thomas Enqvist in four sets. With this win, Kafelnikov became the first Russian, male or female, to win an Australian Open title. In the women's singles, two-time defending champion Martina Hingis successfully defended her title, defeating another surprise finalist in Frenchwoman Amélie Mauresmo. This win allowed Hingis to join Margaret Court, Evonne Goolagong Cawley, Steffi Graf and Monica Seles as the only women to have won three consecutive Australian Open titles. Amélie Mauresmo would later become the World No. 1 in 2004, and despite being one of the top players of the early to mid-2000s, this would be her only Grand Slam final until the 2006 Australian Open, which she won.

In doubles, the defending champions were Jonas Björkman and Jacco Eltingh for the men's, Martina Hingis and Mirjana Lučić for the women's, and Venus Williams and Justin Gimelstob for the mixed. Eltingh did not participate at this year's Australian Open, leaving Björkman to team up with Australia's Pat Rafter. Rafter and Björkman later won the title, defeating the Indian first seeds Mahesh Bhupathi and Leander Paes in five sets. Hingis and Lučić also separated, with Hingis teaming up with Anna Kournikova and Lučić teaming up with Mary Pierce. Lučić and Pierce fell in the first round, but Hingis and Kournikova went on to win, by defeating first seeds Lindsay Davenport and Natasha Zvereva at the final. The mixed doubles competition saw Williams and Gimelstob not competing, and none of the seeds reaching past the second round. In the end, the South African team of Mariaan de Swardt and David Adams won, defeating Williams' sister Serena and her partner Max Mirnyi in the final.

The Juniors Competition saw the first ever junior double, with Kristian Pless and Virginie Razzano both winning their respective singles and doubles titles. Pless defeated Mikhail Youzhny in the singles before teaming up with Jürgen Melzer to defeat the Czech team of Ladislav Chramosta and Michal Navrátil in the doubles. Razzano defeated Katarína Bašternáková in the singles final and teamed up Eleni Daniilidou to defeat South Africans Natalie Grandin and Nicole Rencken in straight sets. The last time a boy won both the singles and doubles title at a Grand Slam was Roger Federer at the previous year's Wimbledon, while the last girl was Cara Black at the Wimbledon the year before. Julien Jeanpierre and Mirjana Lučić were the last players to win Australian Open Junior singles and doubles titles in the same year; in 1998 and 1997 respectively.

There were five competitions open to professional tennis players. The Association of Tennis Professionals and Women's Tennis Association awarded ranking points in all events apart from the mixed doubles. The singles draws were contested by one hundred and twenty eight players, while sixty four teams partook in the doubles events, and thirty two teams lined up in the mixed doubles competition.

With World No. 1 Pete Sampras absent, along with World No. 2 and last year's finalist Marcelo Ríos, the No. 1 spot was thought to be up for grabs coming into this year's Australian Open. Andre Agassi was considered the favourite, having won the 1995 Australian Open and having what was thought to be an easy path to the semifinals, Carlos Moyá being the only player considered to be a threat to him. Patrick Rafter was also considered a favourite, despite having in-form players Thomas Enqvist and Mark Philippoussis in his path. Àlex Corretja was another possibility to claim the No. 1 spot, being the World No. 3 and only a third round appearance to defend.

With Ríos' withdrawal, Àlex Corretja was the top seed at No. 2, with US Open champion Patrick Rafter, French Open champion Carlos Moyá and Andre Agassi following. Tim Henman, last year's semifinalist Karol Kučera, Greg Rusedski, Richard Krajicek and Yevgeny Kafelnikov made up the rest of the top 10 seeds. Despite being the defending champion, Petr Korda was not seeded as he was outside the Top 17.

The first round saw the first upset of the tournament, with Moyá falling to World No. 37 Nicolas Kiefer in four sets. 12th seed Albert Costa, 13th seed Cédric Pioline and 16th seed Thomas Johansson also fell in the first round. Corretja, 15th seed Todd Martin and Korda all survived five set encounters. The second round saw the end of Corretja's No. 1 dreams as went down in four sets to World No. 86 Christian Ruud. Rusedski was also the victim of an upset, falling to qualifier Paul Goldstein also in four sets. The third round saw further upsets, as Rafter fell in four sets to Enqvist, Henman went down to Swiss Marc Rosset in three, and Krajicek went down to Wayne Ferreira in five. The third round also saw the end of Korda, falling to Martin in five sets; and Kafelnikov survive an encounter with 1992 and 1993 champion Jim Courier, Courier having retired in the fourth set.