The Croatia national under-21 football team represents Croatia in international football matches for players 21 or under. It is governed by the Croatian Football Federation, the governing body for football in Croatia. It is a member of UEFA in Europe and FIFA in global competitions. The team's colours reference two national symbols: the Croatian checkerboard and the country's tricolour. They are colloquially referred to as the Mladi vatreni. So far, the Mladi vatreni qualified for five UEFA European Under-21 Championships, namely in 2000, 2004, 2019, 2021 and 2023. Croatia was unable to pass the group stage until the 2021 Euro when it was eliminated in the quarter-finals, its greatest accomplishment in the European competition so far.

The Union of European Football Associations is one of six continental bodies of governance in association football. It governs football, futsal and beach football in Europe and the transcontinental countries of Turkey, Azerbaijan, Georgia and Kazakhstan, as well as the West Asian countries of Cyprus, Armenia and Israel. UEFA consists of 55 national association members. Since 2022, due to the Russian invasion of Ukraine, FIFA and UEFA suspended all Russian national teams and clubs from any FIFA and UEFA competitions.