Wales reached their second straight European Championship finals after a goal in each half by midfielder Aaron Ramsey gave them a 2-0 home win over Hungary in their Group E qualifier on Tuesday.
The Welsh, who reached the Euro 2016 semi-finals, finished runners-up on 14 points from eight games, three behind Croatia who sealed their berth on Saturday with a 3-1 win over Slovakia.
Both sides needed victory to progress and Wales drew first blood when Ramsey rose to head home from six metres in the 15th minute after a perfect Gareth Bale cross from the right.
Wayne Hennessey made a crucial double save to keep Wales ahead in the first half before Ramsey struck again in the 49th with a close-range drive into the top corner after a set piece.
The outcome was a triumph for Wales manager Ryan Giggs, who never featured at a World Cup or European Championship as a player but can now revel in guiding his country to Euro 2020 after taking over from Chris Coleman in January 2018.