The former Crystal Palace boss had been free to join any side after he opted against renewing his contract with the Eagles at the end of the 2025/26 season.
Glasner is set to replace VÃtor Pereira at the City Ground on a three-year contract and has reportedly already discussed transfer plans with Forest ahead of the new season.
The Austrian mentor enjoyed an impressive spell with the Eagles, guiding the club to last season's UEFA Europa Conference League title following the historic FA Cup triumph in 2025 and subsequent FA Community Shield win.
He will become the fifth managerial change at Forest in the past 12 months as the Tricky Trees attempt to launch a long-term project under the 51-year-old.
Glasner will have some funds to work with in the market with the imminent big money transfer of England midfielder Elliot Anderson to Manchester City.