Atkinson replaces Philip Miles, who left the company soon after Titan bought UK operator Maiden Outdoor. He will report to joint managing director Alison Reay, and will oversee a team of 95 working in national sales to agencies, clients and specialists, the creative unit Titan Unique, and the four regional sales offices.
Atkinson has spent the past 16 years with Associated Newspapers. He was head of trading for newspapers until August 2005, when he was promoted to his current role, working with ad director Simon Davies.
Reay said: "Steve brings an enviable wealth of media experience, an entrepreneurial leadership of people, business and strategy that will be crucial for building a successful Titan UK business."
Atkinson said: "I enjoy the job I have at Associated, but it's frustrating waiting for the opportunity to run your own department. And it's a great time to be joining outdoor."
He added that, unlike newspapers, outdoor was not facing a perceived threat from the internet, and the sales job was unfettered by having to worry about content.
The appointment of a head of national sales completes the overhaul of Titan's senior team. Earlier this month, Peter Woodvine and Mark Inskip joined to oversee regional sales.
Woodvine, who joined from customer communications agency Publicis Blueprint, was named regional agency director. Inskip was promoted from within the business to head of direct regional sales.
Titan will mark its takeover of Maiden with a national marketing campaign. The company has created ads featuring photos of famous UK landmarks which spell out the Titan name. These will appear on 500 roadside 48-sheets, 100 rail 48s, and a selection of 96-sheets in major towns and cities across the UK.
Animated versions of the creative will feature on digital screens at mainline railway stations.