Nice secured an eighth-placed league finish last season, missing out on a Europa League spot by a single point.
"Leaving New York is an incredibly difficult decision for me and for my family and one that has not been taken lightly," the 41-year-old told NYCFC's website https://www.nycfc.com/post/2018/06/11/patrick-vieira-departs-new-york-city-fc-join-ogc-nice.
Vieira retired at Manchester City in 2011 and began his coaching career at City's youth team before joining New York and guiding them to successive playoff appearances.
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"Nice were looking for a coach with the ability to continue to produce attractive football, to bring through youngsters by taking risks to help them grow, and someone who lives and breathes to win," President Jean-Pierre Rivere said on the club's website https://www.ogcnice.com.
"This coach is called Patrick Vieira..."
The Frenchman earned 107 caps for his nation and was part of the team that won the 1998 World Cup and the European Championship two years later.
Vieira's assistant coach Christian Lattanzio, performance coach Kristian Wilson and physical performance coach Matt Cook at New York will follow the Frenchman to Nice.
City manager Pep Guardiola's assistant coach Domenec Torrent has left the Premier League champions to take over as the new head coach of New York until the end of the 2020 season.
"Though I have enjoyed a wonderful 11 years working alongside my colleague and close friend Pep Guardiola - it has always been my ambition to manage a team again and I really couldn't have hoped for a better opportunity than at this football club," Torrent said.
New York are currently second in the MLS' Eastern Conference.
Torrent previously managed Italy's Girona FC and was Guardiola's assistant at Barcelona FC and Bayern Munich.
(Reporting By Anirban Paul and Aditi Prakash in Bengaluru; Editing by Christian Radnedge and Pritha Sarkar)
