The 74-bedroom Threadneedles in London and the 65-bedroom Glasshouse in Edinburgh are the new additions to the brand, which currently has more than 40 hotels in the USA, South America, the Caribbean and Europe.
The collection - which includes the Algonquin in New York and Hotel L'Hermitage Gantois in Lille, France - continue to be marketed as independent properties, but they benefit from joining the Marriott Rewards programme and being represented on the Marriott.com website. The Marriott Rewards programme has more than 40 million members worldwide.
Amy McPherson, president and managing director for Marriott International in Europe, said the addition of two hotels in the UK marked "an exciting time" for the Autograph Collection.
"Autograph Collection offers an enviable range of artistic, culinary and cultural adventures for our guests and these two iconic hotels will be valuable additions," she explained.
John License, European brand leader for the Autograph Collection said with the five-star brand, which was launched three years ago, now numbering 42 hotels, there is the potential for significant future growth. "I believe we could have around 50 hotels in Europe and up to 150 worldwide by 2015.
"Independent hoteliers like the brand as it enables them to maintain the unique identity of their properties, while at the same time enjoy the benefits of connecting to our widespread reservations system.
"While the size of hotels in the collection currently range from 15 to 3,000 bedrooms, the average size is around 100. We are not prescriptive in any way in terms of the style, but the main category tends to be iconic and historic buildings, such as former palaces and monasteries. However, we also have modern, boutique hotels, such as the Fontecruz Lisboa in Lisbon, which converted to the brand in December 2012."
License said he expects a further one or two UK hotels will join the Autograph Collection this year.
Threadneedles and the Glasshouse have been owned by the North American-based Westmont Hospitality Group since 2010, when it bought the Eton Group out of administration. Westmont owns more than 500 hotels in Europe, North America and Asia and is one of the largest franchisees of InterContinental and Hilton hotels worldwide.
Threadneeldes is located within a former Victorian banking hall in the heart of the City of London, close to St Paul's Cathedral, while the Glasshouse is built into the 150-year-old faÁ§ade of the Lady Glenorchy church and offers a two-acre roof-top garden used as an event space.
Pictured: The Threadneedles in London (left) and the Glasshouse in Edinburgh