Union SG, short for Royale Union Saint-Gilloise, is a Belgian professional football club based in the Brussels suburb of Forest. Founded in 1897, it is one of the most historically successful clubs in Belgium, having won eleven national titles between 1904 and 1935, a record unbeaten streak of 60 league matches from 1933 to 1935, and recently a twelfth league title in 2025 after a long championship drought. The club plays its home matches at the Joseph Marien Stadium. In recent years, Union SG experienced a strong resurgence after a takeover by British businessman Tony Bloom, who is also chairman of Brighton & Hove Albion. The club returned to Belgium's top division in 2021 and quickly established itself among the top teams, clinching the championship in 2025. Union SG is also known for its loyal fan base, progressive and inclusive values, and a family-friendly stadium environment. They have re- established themselves in European competitions, qualifying for the UEFA Champions League group stage for the first time.