Round-up: now THAT'S how to do a semi-final!
It was a night jam-packed with incredible performances, but only two acts could go through to Sunday's final.
Jules O'Dwyer and Matisse were the big winners of the night, securing the majority of the public vote, while Old Men Grooving and Revelation Avenue were left to battle it out for second and third spot.
Simon took the Judges vote to deadlock, and the decision was back in the great British public's hands, with Old Men Grooving bagging second place, and a ticket to the final.
Check out some of the other jaw-dropping performances of the night here:
These little cutie pies put on a groovy performance with razzmatazz aplenty tonight!
"Wales must be super proud of you! You were super cute, super groovy and so way out," gushed Amanda.
Simon agreed: "You were fantastic tonight! And after last night, Wales is on fire at the moment!"
Jules and Matisse the dog were joined by his best friend Chase in tonight's semi-final act.
"Are they are real dogs?" asked an amazed Simon. " It was fantastic. Honestly, it was amazing. I was absolutely enthralled. It was one of the best dog acts I think we've ever seen!"
"You look amazing. It was an atonishing performance. It was just horrendous to watch, but good!"
Simon: It was fantastic. It was difficult to watch. Some people are going to love this, some people are going to hate this... but it was incredible.
Wow - you're very bendy aren't you! It was a stunning performance, something we've never seen before."
Revelation Avenue didn't disappoint with their pitch perfect rendition of Halo by Beyonce on tonight's semi-final - earning a standing ovation from the Judges and the audience!
"It was just a beautiful interpretation... it couldn't have been better," said Amanda.
And David wants to sign them to DW Records!
Hold On! Yes, The HoneyBuns brought some classic Wilson Phillips to the BGT semi-final.
"We've got Little Mix, now we've got Big Mix - you're six regular fun girls, you don't take yourselves too seriously... it was a killer song by the way!"
Michael Late brought the magic of the Austrian Alps the BGT stage during his semi-final performance.
"That was so random! But I really enjoyed it," said Alesha.
"it was fantastically nuts, the whole thing, " added Simon.
Luca's singing may not have wowed the Judges, but they were mightily impressed by his twerking in platform heels.
"I'll be honest you, this is better than the Eurovision song contest... I started to like it when you were dancing. There's no one quite like you Luca!" admits Simon.
Alison - who sang Climb Ev'ry Mountain from The Sound Of Music - hit all the high notes during her incredible semi-final performance on Tuesday night.
"You've got a big set of pipes on you," gushed Alesha.
Simon had some reservations, but admitted, "you are an amazing singer!"
Old Men Grooving got some serious groove during their semi-final performance - the audience were loving it! And so were the public, voting them the second most popular performance of the night.
"It was pure joy to watch you up there," said David.
Simon said: "You made me want to ovate!" Erm, we quite agree!
Don't forget to tune in to ITV on Wednesday at 7.30pm for the third semi-final.
Groove Thing get their cute on!Jules and Matisse are seeing doubleDancer Bonetics is in bit of a bindAre singers Revelation Avenue on the road to success?Can girl group The HoneyBuns hold on for one more day?Is magician Michael Late just an illusionDancer Luca Calò is crazy in loveSinger Alison Jiear has a dreamHave Old Men Grooving got what it takes?