The 2005 Mercedes Cup was a men's tennis tournament played on outdoor clay courts. It was the 28th edition of the Mercedes Cup, and was part of the ATP International Series Gold of the 2005 ATP Tour. It was held at the Tennis Club Weissenhof in Stuttgart, Germany, from 18 July until 24 July 2005. First-seeded Rafael Nadal won the singles title.
See main article: 2005 Stuttgart Open – Singles. 
Rafael Nadal defeated 
Gastón Gaudio, 6–3, 6–3, 6–4
See main article: 2005 Mercedes Cup – Doubles. José Acasuso / Sebastián Prieto defeated Mariano Hood / Tommy Robredo 7–6(7–4), 6–3