FSV Mainz 05 opened their Bundesliga 2025 campaign with a 0–1 home defeat to 1. FC Köln on Sunday, 24 August 2025, at the start of Matchday 1. The match, which kicked off at 13:30 UTC, was refereed by Tobias Stieler. The only goal of the afternoon arrived in the second half, with both sides going into the interval locked at 0–0.

For a Mainz side aiming to build on their established top-flight status, dropping points at home on the opening weekend was a setback. The result immediately put pressu...