Swansea City completed signing of Ki Sung-Yeung for a club record fee of £5.5 million ($8.6 million) from Scottish giants Celtic.
The 23-year-old, who was also linked with an Arsenal move, signed a three-year-contract with the English Premier League club after completing his medical Friday.
"When I look at Swansea I see a club that is growing and growing, and the style here is very attractive to me," the South Korean international told the club's official website.
"Last year I watched them a lot in the Premier League and they did things very differently to a lot of the other teams. They wanted to keep the ball and pass it around, which I love to do. When they didn't have the ball they worked so hard to get it back quickly.
"It was very impressive, and I think I can grow as a player here and help the club move forward. The manager is another big attraction. I remember watching him when I was younger and I was amazed by how good he was.
"Now I want to learn from him in order to help me become a better player. I learned a lot at Celtic - it helped me become more of an all-round player.
"This is something I have dreamt about since I was a child - playing in the Premier League against the best players in the world. I can't wait to play my first game."
Meanwhile, Matt Jarvis joined West Ham United from relegated Wolverhampton Wanderers for an undisclosed fee, believed to be a little over £10 million, also a club record fee for West Ham.
Jarvis signed a five-year contract, with an option for a further year, and the winger, who has made one appearance for England, will go straight into the first-team and could be in contention for a place in West Ham's match against Swansea Saturday.
"I'm delighted to have signed," Jarvis told the club's official website. "It's a fantastic club and I'm pleased to be here. It's a great club and it's got great history and tradition. I know about Bobby Moore and the history and tradition that go with that.
"I'll be playing with some fantastic players and it'll be great to get into training and I'm looking forward to playing with them. Hopefully I will add a bit of pace, crossing and deliveries that will provide some assists.
"I've been told about how good the fans are hopefully they'll get behind me and I can show them what I can do.
"It'll be straight in and hit the ground running. There's no time to think about it, you've just got to get on with it, which is good. I hope to train with the team today and then travel up to Swansea."
Hammers manager Sam Allardyce has been trailing the 26-year-old all summer, and said he was delighted to finally seal the capture. "From my point of view it is a big piece of business for a terrific young man who will add a lot of quality to our team," Allardyce said.
"Certainly from an attacking sense he is one of the best final-third crossers in the Premier League and his stats were very good at Wolverhampton Wanderers. He delivers in the business end of the field and creates a lot of chances and is a player that can give opposition defences an awful lot of trouble. We are hoping he will produce that for us."