The Union-Rennen is a Group 2 flat horse race in Germany open to three-year-old thoroughbreds.
It is run at Cologne over a distance of 2,200 metres (about 1 mile and 3 furlongs), and it is scheduled to take place each year in June.
It was staged at Grunewald for a short period after World War I, and it returned to Hoppegarten during the 1920s.
The Union-Rennen serves as a trial for the Deutsches Derby, and many horses have won both races.
With its 190th running in 2025, the Union-Rennen is Germany's oldest surviving horse race.