2005 Gerry Weber Open – Singles

Roger Federer was the two-time defending champion, and won in the final 6–4, 6–7(6–8), 6–4, against Marat Safin. With this victory, Federer equalled Yevgeny Kafelnikov's record for three singles titles in Halle; and he became the first to win three consecutive singles titles at the tournament. Federer also won the doubles title, partnering Yves Allegro.

Seeds
• # Roger Federer (champion)

• # 🇷🇺 Marat Safin (final)

• # 🇪🇸 Rafael Nadal (first round)

• # 🇦🇷 Guillermo Cañas (semifinals)

• # 🇦🇷 David Nalbandian (first round)

• # 🇸🇪 Joachim Johansson (first round)

• # 🇩🇪 Tommy Haas (semifinals)

• # 🇪🇸 Feliciano López (second round)