Work on the hotel, which is aimed at the extended-stay business and leisure markets, will begin at the start of next year and is expected to be completed by summer 2017.
It will comprise 114 studios and 12 one-bedroom suites – each with a fully equipped kitchen and separate areas for living and sleeping – a lounge bar, Grab and Go Market, fitness centre and business centre.
The hotel will be the first Residence Inn by Marriott in the city and joins seven other Marriott properties in Scotland including Courtyard by Marriott and Marriott hotels in the Dyce area of Aberdeen and a 107-room Residence Inn by Marriott hotel in the centre of Edinburgh.
Tim Walton, vice president international development, Marriott International said: "We are thrilled to be part of the exciting development plans for Marischal Square as we continue to expand our Residence Inn by Marriott brand in Scotland.
"The brand prides itself on giving guests everything they need to thrive on longer stays, and we are confident that the modern and stylish design of the hotel combined with the excellent location at the heart of Aberdeen will offer a dynamic hotel experience in the city."
Aberdeen City Council leader Councillor Jenny Laing commented: "This agreement is a major boost for the city and highlights the strong appeal of both Aberdeen and the new Marischal Square development to top-flight international businesses.
"Marriott International is one of the world’s leading hotel companies and to see them developing a four-star hotel on the site is a huge vote of confidence in the continuing regeneration of our city centre."
When complete the Aviva Investors-funded Marischal Square will provide office space, retail, cafes, restaurants and civic space on the site once dominated by the former Aberdeen City Council headquarters building St. Nicholas House.
Marriott operates more than 650 Residence Inn properties in the United States, Canada, Europe, the Middle East and Central America. This will be its fourth opening in Europe alongside Residence Inn Edinburgh, Residence Inn Munich City East and Residence Inn Sarajevo.