Trained by Aidan O'Brien, Forever Together was tackling the Oaks at just her fourth start and came into the race off a strong last start second in the Listed Cheshire Oaks.
She relished the longer journey to score a commanding four and a half length win with Donnacha O'Brien in the saddle.
"Forever Together was very impressive. I got a beautiful trip and followed Ryan (Ryan Moore rode Magic Wand to finish fourth), who edged over and gave me a bit of company to the rail. I got on the rail and she's very genuine and galloped to the line. She's a proper staying filly," Donnacha O'Brien said.
Bought for 900,000 euros at the Goffs Orby Yearling Sale by MV Magnier, Forever
Together was the highest priced filly at that sale and second highest overall.She is a full sister to Group I winning filly Together Forever and half-sister to Group I winner Lord Shanakill being from terrific producer Green Room, the dam of seven winners from eight runners.
Forever Together may well add another Oaks to the resume with the Irish Oks a likely next target.
"This is incredible. I am so delighted for everyone," said Aidan O'Brien.
"Forever Together is a staying filly who gets the trip very well and is obviously by Galileo, which is a massive advantage. Donnacha gave her an unbelievable ride. I am over the moon.
"It went according enough to plan. We weren't sure about the ground - who would act on it and who wouldn't. Donnacha rides her in all her work and he was very happy with her after Chester.
"I think we will go to the G1 Irish Oaks now. Obviously we will have to see what the lads want to do, but you'd be thinking she'd love the Curragh. We're very happy with all the fillies, really."
Forever Together is the 71st Group I winner for Galileo.
