EIG, formerly Enterprise Inns, owns over 4,000 pubs across England and Wales.
Stonegate began trading in 2010 after acquiring 333 pubs from Mitchells & Butlers, and now manages an estate of more than 765 sites after a series of acquisitions including the Walkabout brand.
It has invested £350m in to the business over the past nine years and believes the combined group will “be better position to compete effectively in what is expected to be a challenging operating environment for the foreseeable future”.
The acquisition valued EIG at almost £3bn, including its debt and adjusted for the recent disposal of 370 commercial properties.
Robert Walker, chairman of EIG says: "The commercial benefits of combining the companies are compelling. Stonegate is committed to continuing to invest in the business for the future benefit of the combined business, tenants and employees.”
The deal is still subject to shareholder and regulatory approval.
Stonegate previously made a c.£100m bid to take over the Revolution Bars group in 2017, but it was rejected by Revolution's shareholders.