MacKay-Lyons Sweetapple Architects is based in Halifax, Nova Scotia, Canada. The practice works locally and internationally on cultural, academic and residential projects, providing full architectural and interior design services. There are two Partners: Brian MacKay-Lyons and Talbot Sweetapple, and one Senior Associate: Melanie Hayne.

In over 30 years of work, the practice has built an international reputation for design excellence confirmed by over 100 awards, including the Royal Architecture Institute of Canada 2014 Firm Award, six Governor General's Medals and two American Institute of Architects Honor Awards. In addition, the firm's work has been featured internationally in over 300 publications and 100 exhibitions.

Both Partners are active in architectural education, Brian as a full professor and faculty member at Dalhousie University for 30 years, and Talbot, as an Adjunct Professor since 1997, and now a Professor of Practice as of 2013. Together, they have held 18 endowed academic chairs and visiting professorships at leading universities worldwide, such as: The Peter Behrens School of Architecture, Washington University in St. Louis, and Harvard University. They have also given over 200 public lectures on their work worldwide.