In his statement, RIBA President Ben Derbyshire said that the recognition for Grimshaw, who founded Grimshaw Architects in 1980, was "well overdue".
Grimshaw Architects most significant projects include the world renowned Eden Project in Cornwall and the International Terminal at London's Waterloo train station.
Grimshaw, 78, said that he was "thrilled" when he heard the news.
"My life, and that of the practice, has always been involved in experiment and in ideas, particularly around sustainability; I have always felt we should use the technology of the age we live in for the improvement of mankind," the British architect added.
"I would like to thank everyone who has ever worked in the office for contributing to our bank of ideas, and for helping to make it an enjoyable and humanistic place."
RIBA praised Grimshaw for his innovative approach and modernist flair. The medal, which is personally approved by the Queen, is awarded annually to a person or group of people who have significantly advanced the cause of architecture.
"For more than half a century, Sir Nicholas's influence has been exceptional," added Derbyshire.
"He is responsible for an extraordinary number of buildings and infrastructure projects of international significance, and for the continuous development of an architecture, which places technology at the heart of the aesthetic."
Hove-born Grimshaw won the RIBA President's Building of the Year (now the RIBA Stirling Prize) and the Mies van der Rohe Award for European Architecture for the International Terminal at London's Waterloo train station.
Several of his most notable projects are located in the city of Bath, including the Herman Miller Factory in partnership with Terry Farrell, the Bath Spa School of Art and Design, and Thermae Bath Spa. Further afield in Russia he designed St Petersburg's Pulvoko airport.
Grimshaw's nomination was supported by architectural luminaries including Peter Cook, Ted Cullinan, Norman Foster, Frank Gehry, Richard Rogers, Antony Gormley and Jane Priestman. He will be presented with the medal in a ceremony in early 2019.
Last year the Gold Medal was bestowed upon Neave Brown, who passed away just over three months later in January 2018. Previous recipients include the late Zaha Hadid, Sheila O'Donnell and John Tuomey, and Peter Zumpthor.
Main photo is by Rick Roxburgh.