The England-under 19s star was on all of Arsenal, Chelsea, Liverpool, Manchester City and Manchester United's radar after a good season in the Championship.
He was named the LFE Apprentice of the Year for the Championship after making 38 appearances as the Whites finished 15th.
And today he penned a new deal at Elland Road until 2017.
"I’m over the moon, all the hard work this season has paid off I think," he said.
"I’m delighted to sign with Leeds United, I’ve really enjoyed this last season."
Asked if he needed much persuading, Cook replied: "Not at all, I’m enjoying my football and enjoying being here. I’ve got no regrets.
"There was a bit of speculation around it all, but as soon as I was told I was going to be signed, I did it.
GETTY
Lewis Cook for Leeds this season
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"Hopefully a few more signings will be brought in to strengthen the team and next season could be great.
"I’ve been getting a lot of people asking me about my future and hopefully they’ll be happy."
Chairman Massimo Cellino added: "Lewis Cook deserves his new contract, he was one of the most exciting players last season.
"I knew we had a wonderful talent when I first saw him in the summer. At first, I thought he was much older than he was. He plays like he has lots of experience.
"My hope is for him to stay at Leeds for a long time and continue growing with Alex Mowatt, Sam Byram, Charlie Taylor and the others. We don't want to sell."