Newcastle complete deal for Arsenal defender Campbell
But a number of clubs expressed interest in the veteran centre-back and Toon boss Chris Hughton has won the race for his signature.
Campbell, who will wear the No5 shirt at St James' Park, said: "At this stage of my career I couldn't have wished for a better move.
"To join a club such as Newcastle, with its proud tradition, heritage and magnificent support, is absolutely tremendous for me.
"I'd like to thank Chris Hughton for putting his faith in me and aim to repay him and the supporters by giving everything I possibly can to help re-establish this great club in the top tier of English football.
"I just want to play and can't wait to get started. There's a real buzz about the place and that's great.
"I've played at St. James' Park numerous times and always found it a fantastic place to play, there's always a tremendous atmosphere."
Hughton added: "I have known Sol since he was a lad at Tottenham and am fully aware of what he has to offer. That is experience, quality, calm assurance and leadership.
"He's a dedicated professional, a terrific addition to the squad and I look forward to working with him again."