Stephenson, who started in the role on Monday, will also be an executive committee member and report to CEO Andrew Haines. He will be responsible for all external and internal comms.
He replaces Stephen Rooney, who held the role for four years and is taking a career break.
Stephenson joins from energy company Centrica, where he covered the role of group director of comms on an interim contract. He was previously director of corporate affairs at investment banking firm, AXA UK & Ireland. Before this he spent more than two years as director of public relations at the Royal Mail Group.
Stephenson said: "This is an exciting time for aviation, an industry I have always been passionate about, and I look forward to working with the team at the CAA in the years ahead."
Stephenson was a member of the board of the Conservative Party for four years.