Robert Lewandowski scored a hat trick as Borussia Dortmund outclassed Bayern Munich 5-2 in the German Cup final and claimed its first domestic double on Saturday.

Japan star Shinji Kagawa opened the scoring in the third minute before Arjen Robben pulled Bayern level from the penalty spot in the 25th.

Mats Hummels put Dortmund back in front with another penalty in the 41st and Lewandowski grabbed his first goal in first-half injury time.

The Poland striker scored again in the 58th and 81st minutes, ending the contest after Frank Ribery gave Bayern a glimmer of hope in the 75th.

It was Bundesliga champion Dortmund's fifth consecutive win over Bayern, which plays the Champions League final against Chelsea in Munich next Saturday.