Cabaye agreed personal terms with Newcastle last week but had to complete a medical and sign the contract which he did today, the transfer fee being undisclosed.
The four-time France international said he was delighted to be joining Newcastle and is looking forward to becoming a part of such a big club.
"This is a fantastic move for me. I have enjoyed great times with Lille but the time is right now to test myself against the best and playing for Newcastle United in the Premier League does just that," Cabaye said.
"My first impressions of the club and the city are that it is a lovely place and the stadium is magnificent.
"Now that I have signed I am looking forward to meeting the rest of the team, working with Alan Pardew and his staff, but most of all playing for Newcastle United and their supporters."