The site was sold by drinks company Diageo, which has owned and developed the hotel since 1984, following several months of talks.
Ennismore, which operates two boutique London hotels under The Hoxton group brand, said it plans to run Gleneagles as a standalone business.
“We will be proud guardians of this asset, ensuring that the service-levels and visitor experience for which Gleneagles is renowned are preserved and enhanced in years to come,” commented Sharan Pasricha, founded and chief executive of Ennismore.
The group will retain the existing hotel management and staff, as well as investing ‘significant sums’ across the estate to further build on the resorts' reputation.
Situated in 850 acres of grounds Gleneagles features over 230 rooms, award winning spa facilities, a two-Michelin starred restaurant, three championship golf courses, and luxury lodges.
The site hosted the G8 summit in 2014 and the Ryder Cup in 2014 – attracting over 250,000 visitors.
The acquisition coincides with the next phase of Ennismore’s £500m international hotel expansion, with sites set to open in Amsterdam this year, Williamsburg, New York in 2016, Paris in 2017, and London, Southwark in 2017.
The group also operates a standalone restaurant division, with three new openings planned for 2015 – including a joint venture with Soho House for two standalone restaurants.
Diageo will retain a relationship with Gleneagles which will see its drinks brands continuing to be showcased at the hotel.