The 31-year-old Wales international had been on Juventus’ books since exiting Arsenal in 2019.
Ramsey’s time in Turin was underwhelming, leading to his contract with Juve being mutually terminated last week.
Ambitious Nice have landed Ramsey, who wants a new challenge ahead of the 2022 World Cup where Wales will compete for the first time since 1958.
Ramsey, who spent six months on loan at Rangers last season, is understood to also have had an option to join MLS club Charlotte FC.
Nice finished fifth in Ligue 1 last term and coached by former Borussia Dortmund boss Lucien Favre, who took over from Christophe Galtier who left for Paris Saint-Germain.
The French club have also recently signed goalkeeper Marcin Bulka, Badredine Bouanani, Rares Ilie and Alexis Beka Beka.
Ramsey only managed 70 appearances across two-and-a-half years with the Bianconeri, netting six goals.
He played 13 games for Rangers, scoring twice, but missing the decisive penalty in the Europa League final shootout loss to Eintracht Frankfurt.