The 2004 Australian Open was a Grand Slam tennis tournament held in Melbourne, Australia from 19 January to 1 February 2004. Andre Agassi was unsuccessful in defending his 2003 title, being defeated in the semi-finals by Marat Safin. This ended a 26-match winning streak for Agassi at the Australian Open, having previously won in 2000, 2001 and 2003, missing 2002 through injury. Roger Federer won his first Australian Open title, defeating Safin in the final. Serena Williams was unable to defend her 2003 title after withdrawing from the tournament due to a left knee injury. Justine Henin-Hardenne defeated compatriot and rival Kim Clijsters in the final to win her only Australian Open title.

Seniors

Men's singles

Roger Federer defeated 🇷🇺 Marat Safin, 7–6(7–3), 6–4, 6–2

Women's singles

🇧🇪 Justine Henin-Hardenne defeated 🇧🇪 Kim Clijsters, 6–3, 4–6, 6–3

Men's doubles

🇫🇷 Michaël Llodra / 🇫🇷 Fabrice Santoro defeated 🇺🇸 Bob Bryan / 🇺🇸 Mike Bryan, 7–6(7–4), 6–3

Women's doubles

🇪🇸 Virginia Ruano / 🇦🇷 Paola Suárez defeated 🇷🇺 Svetlana Kuznetsova / 🇷🇺 Elena Likhovtseva, 6–4, 6–3

Mixed doubles

🇷🇺 Elena Bovina / Nenad Zimonjić defeated 🇺🇸 Martina Navratilova / 🇮🇳 Leander Paes, 6–1, 7–6(7–3)

Juniors

Boys' singles

🇫🇷 Gaël Monfils defeated 🇫🇷 Josselin Ouanna, 6–0, 6–3

Girls' singles

🇮🇱 Shahar Pe'er defeated 🇨🇿 Nicole Vaidišová, 6–1, 6–4

Boys' doubles

🇺🇸 Scott Oudsema / 🇺🇸 Brendan Evans defeated 🇦🇺 David Galić / 🇦🇺 David Jeflea, 6–1, 6–1

Girls' doubles

Chan Yung-jan / 🇨🇳 Sun Shengnan defeated 🇨🇿 Veronika Chvojková / 🇨🇿 Nicole Vaidišová, 7–5, 6–3

Wheelchair

Men's singles

🇦🇺 David Hall defeated Robin Ammerlaan, 6–4, 7–5

Women's singles

Esther Vergeer defeated 🇦🇺 Daniela Di Toro, 4–6, 6–3, 6–1

Men's doubles

Robin Ammerlaan / 🇦🇹 Martin Legner defeated 🇵🇱 Tadeusz Kruszelnicki / 🇯🇵 Satoshi Saida, 6–3, 6–3

Women's doubles

Maaike Smit / Esther Vergeer defeated Sonja Peters / Sharon Walraven, 6–3, 7–6(3)