Since turning professional in 2017, the 25-year-old Scot won his first European Challenge Tour title on what was just his fifth start at the NI Open, presented by Modest! Golf.
That result earned him full Challenge Tour playing privileges in 2019, when he won twice – at the Euram Bank Open and the Made in Denmark Challenge.
As brand ambassador, Calum will wear the GAC logo during tournaments and will also attend corporate client events.
“We are delighted to welcome Calum to our team, he is certainly an exciting prospect and we have always believed in investing for the future,” said Stuart Bowie, Group Vice President Commercial for GAC.
Calum joins three other golf professionals signed by GAC – South Africa’s George Coetzee, Denmark’s Nicole Broche Larson and India’s Shiv Kapur.
“I am excited to join the GAC team as their latest brand ambassador,” said Calum, who is playing in this week’s Saudi International powered by Soft Bank.
“This year will be my first full season on the European Tour and I am really looking forward to the challenge.
“This is a very important stage in my professional journey and I am grateful to GAC for their support.”
Six-time Match Racing World Champion sailor Ian Williams is also an ambassador for GAC.