The Rossoneri have been desperately searching for a centre back in recent weeks following the injury to key man Alessandro Nesta.
With Dario Simic and Digao both being offloaded, things started to become desperate for the Rossoneri when primary target Branislav Ivanovic, who had seemed certain to join from Chelsea, saw his transfer fall through at the last moment.
It was reported last week that Milan had turned their attentions to another Premiership based player, in the form of Arsenal centre back Philippe Senderos, and the deal has now been officially completed.
The Swiss centre back arrives on a one year loan deal, and Milan have the option to make the move permanent for a set fee next summer.
Senderos had been well down the pecking order at Arsenal following an error-prone season last term, and Arsene Wenger signalled his intention to let him leave after signing Manchester United’s Mickael Silvestre last week.
The 23-year-old Senderos made 74 Premiership appearances, scoring four goals, since signing for Arsenal from Servette in December 2002.
He has won 31 caps for Switzerland, playing at World Cup 2006 and Euro 2008.