Germany striker Lukas Podolski will join Arsenal for an undisclosed fee.
The Cologne star, who has also played for Bayern Munich, said: "I'm so happy to be joining Arsenal and the Premier League. They are one of the top clubs in Europe with a huge history."
Podolski, 26, has scored 43 goals in 95 internationals, putting him joint-sixth on Germany's all-time list.
Arsenal boss Arsene Wenger said: "That is a phenomenal record and just shows his quality as a player."
Podolski, who has 95 caps, added: "There are many top-quality players at Arsenal and their style is fantastic.
"I have made this decision not against FC Cologne but because it is a great opportunity.
"This was not an easy decision for me at all, as Cologne, our fans and the city are something special for me."
The Poland-born forward, who had one year left on his contract, has scored 18 league goals this season for a side battling relegation, which is his best ever top-flight return.
He added: "I will always carry FC Cologne in my heart. We need to pool our strengths now and have to be fully focused on our survival in the Bundesliga."
Wenger added: "He is a top-class player, a very good finisher and a proven performer at club and international level. He is a very strong player and will provide us with good attacking options."
Arsenal are looking to add to their striking options. While although Robin van Persie has netted 28 to become the Premier League's leading scorer, their next highest scorer is Theo Walcott on eight goals.
Podolski, who will link up with international team-mate Per Mertesacker in north London, played for Germany at the 2006 and 2010 World Cups and is set to be part of their squad at Euro 2012.
Cologne's executive chairman Claus Horstmann said: "Cologne were prepared to extend Lukas Podolski's contract on the basis of a competitive offer. Nonetheless, this early transfer decision offers scope and planning security for the next season.
"Lukas has left a mark on FC Cologne's reputation and we feel the need to thank him for numerous great football experiences."