The 55-key aparthotel joins the brothers' portfolio of hospitality venues in the city, which also includes the Town Square bar and restaurant, Victoria Apartments Belfast, and the 1852, a hotel due to open within the former Crescent Townhouse later this year.
Peter Rhineland said: "The Flint model is an amalgamation of our experience in the serviced apartment business and the hotel business. Each unit is essentially a hotel room with a small kitchen, allowing guests to stay that bit longer. We believe that corporate hotels don't have to be 'corporate' and have tried to leave as much character in the building as possible."
The Flint is housed in a 1923 former Presbyterian War Memorial building, which has retained many of its original features. The interior design was led by architect Sarah McLorn with most of the furniture made by Terry Design and Rui Design. Each suite has a king-sized bed, sofa area, small kitchen and a bathroom.
A 220-cover rooftop bar will be added at a later date.