Mark Flekken was born on 13 June 1993 in Kerkrade, Netherlands, and developed through several lower-division German clubs before establishing himself at top-tier level. After spells at Alemannia Aachen, SpVgg Greuther Fürth and MSV Duisburg (where he made 68 appearances), he joined SC Freiburg in 2018 and spent five seasons there, becoming the primary goalkeeper after returning from a 2020-21 elbow injury.
In May 2023 Brentford signed him for around £11 million, and across two Premier League seasons he made 74 league appearances, becoming one of only two goalkeepers in 2023-24 to register an assist. In 2024-25 he led the Premier League in saves with 153 and posted a 73.6% save percentage. In June 2025 Bayer Leverkusen signed him on a three-year deal worth around €10 million.
For the Netherlands, Flekken was selected for the Euro 2024 squad and continues to be a senior international option.
Standing 1.94 m, Flekken is a tall, modern goalkeeper with elite reflexes and confident distribution — exactly the profile Leverkusen wanted to refresh their goalkeeper room around alongside Janis Blaswich after the post-Lukáš Hrádecký years.