Newcastle clinched a four-year deal for Portsmouth's Amdy Faye on Wednesday for a fee believed about £2m.
The Senegalese international, 27, who joined Portsmouth from Auxerre in 2003, had also been linked with moves to Middlesbrough, Aston Villa and Bolton.
Faye becomes the third January signing for Graeme Souness after Jean Alain Boumsong and Celestine Babayaro.
"We are delighted to have him on board and he will be a really valuable addition to our squad," said Souness.
Faye made a total of 52 appearances for Pompey, and can play in Saturday's FA Cup tie with Coventry.