Liverpool star came off the bench to score twice.
Liverpool beat Barcelona 4-0, scoring three times in the second half.
Wijnaldum was a half-time substitute, replacing Andy Robertson, who picked up an injury. He went into midfield with James Milner slotting into defence.
The Dutchman scored twice midway through the second half, and admits he was upset to have been benched for the fixture.
He told BT Sport's live coverage: ""Unbelievable. After the game in Spain we were confident we could score four and win 4-0. People outside doubted us and thought we couldn't do it. But once again we showed everything is possible in football.
"I was really angry that the manager put me on the bench. I just tried to help my team, I’m happy I could do that with two goals."
Wijnaldum has written himself into Liverpool folklore with his brace, along with teammate Divock Origi.
Whatever happens in the final, Liverpool's win last night will be remembered for a long, long, time.
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