2003 WTA Tour Championships – Singles

Defending champion Kim Clijsters successfully defended her title, defeating Amélie Mauresmo in the final, 6–2, 6–0 to win the singles title at the 2003 WTA Tour Championships. It was her second Tour Finals title, her ninth title of the season, and the 19th of her career.

Seeds
• # (1) 🇧🇪 Kim Clijsters (champion)

• # (2) 🇧🇪 Justine Henin-Hardenne (semifinals)

• # (5) 🇺🇸 Jennifer Capriati (semifinals)

• # (6) 🇫🇷 Amélie Mauresmo (final)

• # (8) 🇷🇺 Anastasia Myskina (round robin)

• # (9) 🇷🇺 Elena Dementieva (round robin)

• # (10) 🇺🇸 Chanda Rubin (round robin)

• # (11) 🇯🇵 Ai Sugiyama (round robin) Note:
 * 🇺🇸 Serena Williams had qualified but pulled out due to left knee surgery.
 * 🇺🇸 Lindsay Davenport had qualified but pulled out due to left foot surgery.
 * 🇺🇸 Venus Williams had qualified but pulled out due to abdominal injury.

Alternates
• # 🇷🇺 Nadia Petrova (not used)

• # 🇷🇺 Vera Zvonareva (not used)

Red group
''Standings are determined by: 1. number of wins; 2. number of matches; 3. in two-players-ties, head-to-head records; 4. in three-players-ties, percentage of sets won, or of games won; 5. steering-committee decision.''

Black group
''Standings are determined by: 1. number of wins; 2. number of matches; 3. in two-players-ties, head-to-head records; 4. in three-players-ties, percentage of sets won, or of games won; 5. steering-committee decision.''