Tottenham booked a showdown with Liverpool in Madrid on June 1 as hat-trick hero Lucas scored in the 96th minute to complete a sensational comeback in Amsterdam.
Trailing 1-0 heading into Wednesday's return leg, Tottenham fell 3-0 behind on aggregate after quickfire goals from Matthijs de Ligt and Hakim Ziyech put Ajax on the brink in the first half.
However, Lucas gave Tottenham hope with two goals in four minutes approaching the hour-mark and he broke Ajax's hearts after steering home the dramatic winner in stoppage time as Spurs prevailed on away goals.
— Tottenham Hotspur (@SpursOfficial) May 8, 2019
"It is impossible to explain what I am feeling in this moment," Lucas told BT Sport. "I am very, very happy, very, very proud of my team-mates
"We always believed in this moment. We always believed it was possible and we gave everything on the pitch. I think we deserved this moment.
"We are a family. It is impossible to explain. I am so happy. It was a big gift from God and I would like to share it with my team-mates, my family and all my friends
"It's not only me. It is my team-mates and teamwork. It is too difficult to play here against Ajax. They played very well.
"But we have a lot of qualities, even without key players we did really well. I am very proud. That's our team. That's our family and we need to fight in all the games like this.
"Football is amazing. It gives the moments like this that we cannot imagine. We need to enjoy it, it is a big moment, the best moment in my career.
"I only need to say thank you to my team-mates because what I am living here at Tottenham is unbelievable. I am so happy."
Photo Getty Images. Caption: Tottenham star Lucas Moura celebrates his hat-trick