Former Crystal Palace manager Glasner will take charge at Forest after Vitor Pereira was sacked last week despite guiding the side to Premier League safety last season.
The 51-year-old Glasner led Palace to their first major trophy in his first season in 2024 – the FA Cup – before winning the Europa Conference League last season.
He announced in January hat he would be leaving the London club to seek a new a challenge and Forest have pounced for his signature.
Marinakis said: “In our discussions with Oliver, it was clear that we share the same vision, the same ambition and the same relentless desire to succeed.
“He has consistently demonstrated throughout his career that he can build outstanding teams and deliver success against the strongest competition.
“It has always been our goal to establish Nottingham Forest once again among the leading clubs in England and Europe. Our ambition is not simply to compete – our ambition is to win, to challenge for major honours and to create a football club that our supporters can be proud of for many years to come.
“Oliver is a winner. He has earned success through his leadership, his personality and the style of football his teams play. We believe he is the right person to lead us into this next chapter.”
On joining Forest, Glasner said: “From my very first conversations with the owner and the leadership team, it was evident to me that they have a clear vision for this football club and complete trust and belief in me and my staff to build a strong future together over the long term.
“That trust and shared commitment, together with the potential that I see within the squad, were key factors for me and I am excited about what we can achieve together.”
