The Zimbabwean, of Scottish descent, has a wealth of experience in senior roles across both cricket and rugby and previously won three ODI caps for his nation.
He was formerly the chief executive of Sussex County Cricket Club and the London Bronces, while he was also managing director of Surrey County Cricket Club and the Worcester Warriors.
His hiring brings to an end what Cricket Scotland have described as a "worldwide" search for the successor to Malcolm Cannon, who resigned in July of this year.
Mackay said: “This is an exciting time for the game in Scotland and I am delighted to have been appointed Chief Executive of Cricket Scotland. I have been impressed with the clear vision, strategy and more importantly, commitment of the board to achieve full member status of the International Cricket Council. This will help us achieve our vision to make cricket mainstream in Scotland and thereby ensure the long term sustainability of the game here.
“Clearly cricket in Scotland is progressing in the right direction for both the men’s and women’s game, as demonstrated by the ICC rankings, while Scotland is regarded as one of the top Associate Countries.
“I look forward to working with all the stakeholders involved in the game from colleagues, clubs, schools, regional associations, supporters, volunteers and commercial partners to drive a bottom up approach to achieving our goals in the new strategy.
“These are exciting times for everyone involved in our great game in Scotland and I really look forward to getting started!”
Tony Brian, chair of Cricket Scotland, added: “It is of great benefit for cricket that we have attracted someone of Gus’s calibre and experience to join us as our new Chief Executive.
"He has wide experience of leading all aspects of sports from growing participation numbers and supporting clubs to running professional teams at a high level.
“We are currently finalising an ambitious strategy which aims to make cricket one of the mainstream sports in Scotland over the next ten years, with a wide increase in participation and which sees us becoming a full member of the International Cricket Council within the next five.
"Gus’ proven skills as a leader of sports bodies and his wide network of contacts throughout the cricketing world make him the ideal person to lead cricket in Scotland through the next, and exciting, phase of our development.”