The undisclosed fee is believed to be in the region of £2.7 million for the 28 year old striker who netted an impressive fifteen goals in La Liga last season.
Kone has been allocated squad number 2, the only number free under 32, and cannot wait to get started.
Speaking to the club's official website, Kone said: “I’m very happy to be here and I’m doubly happy because I know how hard the manager has had to fight to get me here.
Kone's signing comes just days after teh announcement that Arsenal's Ryo Myaichi has joined on a season long loan deal.
Aligned with the additions of defender Ivan Ramis and midfielder Fraser Fyvie, the Latics have a strong summer's business behind them.
Roberto Martinez has yet to comment as to whether this summer's business is complete and further signings may well be made before the close of the transfer window.