Ennismore is believed to have bought Eynsham Hall country house hotel in Oxfordshire.
The Times reports Ennismore, the owner of Gleneagles in Auchterarder and the Hoxton hotel brand, has bought the 135-bedroom property.
The hotel was brought to market earlier this year by Christie & Co with an asking price of £8.25m. Christie & Co confirmed the property has been sold but did not confirm the buyer.
Owner Richard Upton, co-founder of Cathedral Group, acquired Eynsham Hall in 2005 and has invested over £3m refurbishing the site. He said he was "not in a position to dedicate the time to take Eynsham Hall to the next stage".
Planning consent has been granted to add 80 guest bedrooms and purpose-built conference facilities, as well as a new spa and swimming pool complex. The Grade II-listed property was rebuilt in 1908 and designed by architect Sir Ernest George.
Ennismore declined to comment.