Ba, who will be eligible for selection for tomorrow’s FA Cup third-round match at Southampton, will wear the number 29 shirt.
‘It feels good to be here, I’m very happy and very proud” said Ba.
‘When the club who won the Champions League wants you, the decision is very easy. This club is massive and that’s something that helped the decision a lot. It was not a hard one.
‘It was important for me, and for Newcastle, to get my future sorted and now we can move on. Now they have the whole month to buy someone and for me as well, the sooner the better. Now I am here I just need to get settled in.’
Ba is joint-third in the Premier League scorers table this season with 13 goals so far and he will allow Rafa Benitez to finally give under-fire striker Fernando Torres a break. Chelsea went into this season with only two strikers in their squad, and with Daniel Sturridge missing most of the season through injuries, Torres has had to play almost every game. And he looks exhausted.