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.

The event was established in 1834, and it was originally held at Tempelhof on the site of what became Berlin Tempelhof Airport. It was initially contested over 2,400 metres, and it was extended to 2,800 metres in 1837.

The race was transferred to Hoppegarten in 1868, and it was cut to 2,200 metres in 1888. It was staged at Grunewald for a short period after World War I, and it returned to Hoppegarten during the 1920s. It was abandoned in 1945 and 1946, and it moved to Cologne in 1947.

The Union-Rennen serves as a trial for the Deutsches Derby, and many horses have won both races. The first was Schwindler, a joint winner of the Derby in 1875. The most recent was Sea The Moon in 2014.

With its 189th running in 2024, the Union-Rennen is Germany's oldest surviving horse race.

• List of German flat horse races

• Racing Post:
  • 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
  • 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
  • 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017
  • 2018, 2019, 2020, 2021, 2022, 2023

• galopp-sieger.de – Union-Rennen.
• horseracingintfed.com – International Federation of Horseracing Authorities – Union-Rennen (2016).
• pedigreequery.com – Union-Rennen – Köln.