The France international moves to the Emirates Stadium to replace countryman Bacary Sagna, who signed for Manchester City upon the expiration of his contract in June.
Debuchy joined Newcastle from Lille in January 2013 and made 46 appearances for the St James' Park club, scoring once.
He has firmly established himself as Didier Deschamps' first-choice right-back at international level and featured in four of France's five fixtures at the FIFA World Cup.
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