Marriott International is expected to double in size in Europe once its $12.2b (£8b) acquisition of Starwood Hotels & Resorts Worldwide is complete.
The deal will create the world's largest hotel company and will see Marriott's size increase to more than 123,000 rooms in Europe. Starwood's 40,500 open rooms will join Marriott's 61,000 open rooms, along with a combined pipeline of 21,500 rooms.
Amy McPherson, president and managing director, Marriott International, Europe, said: "It's been an extraordinary time for Marriott. We signed more than 10,000 new rooms in 2015 for the first time in our history, doubling in size since 2010.
"Added to this unprecedented growth was the announcement of our Starwood acquisition which is expected to close in mid-2016. Our momentum is incredible."
The merger of the two US companies involves an unprecedented 30 brands, bringing together the likes of Ritz-Carlton, Edition and Moxy from Marriott alongside St Regis, Sheraton and W Hotels from Starwood.
Marriott's AC Hotels, the urban European design hotel brand, which was recently introduced in the US, will launch in the UK for the first time in Manchester and Birmingham in May. The Moxy Hotels brand is also expected to open its first UK hotel in Aberdeen.
With more than 4,400 rooms scheduled to open this year, Marriott's Central and Eastern regions should account for over 70% of Marriott's total European development.
In the UK, the London Marriott Hotel County Hall and Grosvenor House, a JW Marriott Hotel, two of Marriott's most iconic London hotels, should complete major renovations by spring of this year.
Marriott operates and franchises hotels and licenses vacation ownership resorts under 19 brands worldwide.