2003 WTA Tier I Series Singles Singles

| Tournament | Surface | Week | Winner | Finalist | Semifinalists |
|---|---|---|---|---|---|
| Tokyo | Carpet (i) | January 27 | Lindsay Davenport 6–7(6), 6–1, 6–2 | Monica Seles | Chanda Rubin Lisa Raymond |
| Indian Wells | Hard | March 3 | Kim Clijsters 6–4, 7–5 | Lindsay Davenport | Conchita Martínez Jennifer Capriati |
| Miami | Hard | March 17 | Serena Williams 4–6, 6–4, 6–1 | Jennifer Capriati | Kim Clijsters Chanda Rubin |
| Charleston | Clay | April 7 | Justine Henin-Hardenne 6–3, 6–4 | Serena Williams | Lindsay Davenport Ashley Harkleroad |
| Berlin | Clay | May 5 | Justine Henin-Hardenne 6–4, 4–6, 7–5 | Kim Clijsters | Jennifer Capriati Amélie Mauresmo |
| Rome | Clay | May 12 | Kim Clijsters 3–6, 7–6(3), 6–0 | Amélie Mauresmo | Serena Williams Ai Sugiyama |