Mykhailo Mudryk has joined Chelsea from Shakhtar Donetsk in a deal worth £88.5m.
The Ukrainian winger previously indicated Premier League leaders Arsenal was his preferred destination.
Then Chelsea agreed to a deal with Shakhtar on Saturday night and then he travelled to west London.
Chelsea confirmed the transfer in a statement and Mudryk has signed an eight-and-a-half-year deal.
He will reportedly earn £100k-a-week at Chelsea with Arsenal believed to only be willing to offer £50k.
The winger told club media: “I’m so happy to sign for Chelsea.
“This is a huge club, in a fantastic league and it is a very attractive project for me at this stage of my career.
“I’m excited to meet my new teammates and I’m looking forward to working and learning under Graham Potter and his staff.”
With Chelsea struggling in the Premier League, owner Todd Boehly seems hell-bent on spending his way out of trouble.
Boehly said: “We are delighted to welcome Mykhaylo to Chelsea. He’s a hugely exciting talent who we believe will be a terrific addition to our squad both now and in the years to come.
“He will add further depth to our attack and we know he’ll get a very warm welcome to London.”
Potter detailed why he was keen to sign the winger, who he believes will “excite” supporters.
“I think you’re never surprised in the transfer window because things happen sometimes like you don’t expect them to happen,” said the head coach.
“In terms of what he brings, he’s a young player with a big future. Exciting one vs one, he attacks the backline, and can go in wide areas but also affects the goal.
“He’s a really exciting player and I think our supporters will really like him.”
