Born in Russia but resides in Germany, Robert Stieglitz began his professional career in 2001 defeating Petr Pokorny by unanimous decision. Stieglitz went on to knock out nine of his first twelve opponents. Only a year in to his professional career, he won the vacant IBF Youth Light Heavyweight title. After making three successful defenses, he vacated his title and went down to the Super Middleweight division. On February 2004, he defeated Galen Brown by technical knockout for the vacant IBF Youth Super Middleweight title. His first world title opportunity came against Alejandro Berrio for the vacant IBF Super Middleweight title but he came up short, losing by technical knockout in the 3rd round. Two years later (2009), Stieglitz got another shot, this time against Karoly Balzay for the WBO Super Middleweight title. Stieglitz won by technical knockout in the 11th round.
Lost his title in a 12-round unanimous decision against Arthur Abraham on August 25, 2012.
On March 23, 2013 regained his title against Arthur Abraham by Technical Knockout in the four round at the GETEC Arena, Magdeburg, Germany
1. IBF Youth Light Heavyweight Champion
2. IBF Youth Super Middleweight Champion
3. IBF Inter-Continental Super Middleweight Champion
4. WBC International Super Middleweight Champion
1. WBO Super Middleweight Champion