Arcop (Architects in co-partnership) is an architectural firm based in Montreal, renowned for designing major projects in Canada. The successor to the firm of Affleck, Desbarats, Dimakopoulos, Lebensold, Sise formed by partners Ray Affleck, Guy Desbarats, Dimitri Dimakopoulos, Fred Lebensold and Hazen Sise, the company adopted the name Arcop in 1970. At its peak in early 1966, it employed over 150 people.
Their first major commission was the Queen Elizabeth Theatre in Vancouver. Subsequent projects would include Salle Wilfred-Pelletier, Place Bonaventure, and Maison Alcan.
In 2011, Arcop and Montreal-based engineering consulting firm Genivar announced a strategic alliance.