The 20-year-old France youth international has been unveiled as the Magpie's fourth recruit from Ligue 1 of the transfer window, with Toulouse midfielder Moussa Sissoko also on his way.
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"It was the desire of the club to sign me up which was the most important factor," he told the club's official website. "It was nothing to do with the league position.
"It was really all about the club's desire and willingness to sign me up. Also, I like the club's ambition to strengthen the whole team so we can improve our league position. That's what appealed to me so I didn't hesitate."
Newcastle manager Alan Pardew was delighted with his new recruit, explaining: "Massadio is very highly-thought of in France and he's somebody who our scouting team have been greatly impressed by.
"At the age of 20, he will only continue to get better but he's already played a lot of games in his country's top division and represented France at under-19, under-20 and under-21 level.
"He's strong and quick and we're looking forward to seeing him develop here."
Haidara joins Mathieu Debuchy, Mapou Yanga-Mbiwa, Yoan Gouffran and Moussa Sissoko in leaving France to join a club with an already healthy contingent of Francophone players, such as Yohan Cabaye, Hatem Ben Arfa, Sylvain Marveaux and Papiss Cisse.