As first reported by Sky News,the pubco started a consultation with 800 employees about a redundancy process earlier today (7 October).
It is understood the company will seek to redeploy affected staff wherever possible.
In total, 79 of Greene King's pubs and restaurants will close, with roughly 25 of those closures - including 11 Loch Fyne restaurants - expected to be permanent.
Greene King's UK estate includes almost 1,700 managed pubs and 1,000 tenanted venues.
The redundancies represent a small fraction of the group's 38,000-strong workforce, but further underline the anxiety of employers grappling with greater operating restrictions imposed on them by a Government that's preparing to end its Job Retention Scheme at the end of this month and replace it with the less popular Job Support Scheme.
In a statement, a spokesperson for Greene King said: "The continued tightening of the trading restrictions for pubs, which may last another six months, along with the changes to government support was always going to make it a challenge to reopen some of our pubs.
"Therefore, we have made the difficult decision not to reopen 79 sites, including the 11 Loch Fyne restaurants we announced last week.
"Around one-third will be closed permanently and we hope to be able to reopen the others in the future.
"We are working hard with our teams to try and find them a role in another of our pubs wherever possible.
"We urgently need the Government to step in and provide tailored support to help the sector get through to the spring and prevent further pub closures and job losses."
Last month it was reported that Greene King’s revenues were down 13.4% to £1.9bn in the full year to 26 April 2020, with its pub business worst hit by the Coronavirus.
The news comes a week after fellow pubco Fuller’s announced that the downturn caused by Government advice to work from home where possible meant it would have to lay off 'at least' 10% of its 5,000-strong workforce.