John Campbell Merrett (August 26, 1909 – November 3, 1998) was a Canadian architect whose most noteworthy work was the interior design of Montreal's Central Station.
Merrett graduated in 1931 from the School of Architecture at McGill University and subsequently did formative work traveling on scholarship in Europe.
From 1936 to 1942 Campbell was staff architect for the Canadian National Railway, for whom he designed the concourse of Montreal's Central Station.
His projects included the town plan of Pointe Claire, Quebec, as well as buildings for regional school boards, universities and pharmaceutical companies.
His real joy came from the many expansion projects at Montreal's Royal Victoria Hospital and much of the modern skyline of that institution can be attributed to him.