Robert Hoyzer (born August 28, 1979 in Berlin, Germany) is a former football referee who scandalized German football by fixing matches.

Hoyzer, a member of the Bundesliga's Hertha BSC Berlin was registered by the German Football Association (DFB) as a referee in 2003. He refereed in the second division and regional leagues but was not selected to officiate in the top division.

Hoyzer's career as a referee came to an abrupt end in January 2005 after he was suspected of betting on a first-round German Cup tie between regional league side Paderborn and Bundesliga club Hamburger SV on August 21, 2004. In the match, HSV took a 2-0 lead, but Hoyzer sent off HSV striker Emile Mpenza in the first half, and later awarded Paderborn two questionable penalties. Paderborn went on to win 4-2.

Hoyzer resigned as a referee and resigned his membership with Hertha Berlin. The DFB soon announced that it was investigating whether or not Hoyzer fixed other matches in the regional leagues and second division. The German prosecutor's office in Braunschweig launched a separate investigation.

Hoyzer initially denied the allegations, but later admitted to them on January 27. It was revealed that Hoyzer had ties to Croat organized crime syndicates who had bet large sums on the matches Hoyzer officiated. German media have reported that Hoyzer told investigators that he was present when other referees received payoffs from the syndicates and had heard that players were being paid as well. On January 28, four arrests linked to the Hoyzer probe were made in Berlin; one of the sites was the café where Hoyzer allegedly met with his contacts. A Stuttgart newspaper also reported that the DFB president said players could have been involved in the fix.

On February 2, prosecutors in Berlin announced that police had raided the premises of 19 suspects in the spreading scandal, and discovered evidence that may implicate as many as 25 people, including 14 players and three other referees, in fixing ten matches in 2004 alone. Hoyzer, who has been cooperating with the German authorities, provided much of the information that led to the raids.

On February 10, the DFB announced that Hoyzer had been officially suspended for "unsportsmanlike conduct", pending a formal hearing that could result in a lifetime ban. He also faces possible criminal charges that could carry a prison sentence of 10 years.

On February 12, Hoyzer was arrested by police after new evidence emerged to suggest that he had fixed more matches than he had already admitted to. The German prosecutor's office has suggested that he faces a long jail sentence if found guilty.

His information has so far led to the arrest of one other person, Dominik Marks , another referee.

On March 24, the German newsmagazine Der Spiegel broke a story that expanded the scope of the scandal far beyond Germany, and possibly to UEFA headquarters. According to the report, Hoyzer told investigators that the gambling ring had the lists of referees and assistants who would work competitive international matches and fixtures in the UEFA Champions League and UEFA Cup about a week in advance of the matches. UEFA does not publicize the officials list until two days before matches. The story also noted that only the UEFA referee manager and the 11 members of its referee commission were supposed to have advance knowledge of these names.

Hoyzer's actions have led the DFB to adopt new policies to prevent further such incidents, including a ban on betting by referees and assigning referees to matches with only two days' notice.