Tempest is currently the sales and marketing director for Whitbread's hotels and restaurant division and oversees the company's budget hotel brand, Premier Inn
He will take up his new role in December and will report directly to Carnival UK's chief executive, David Dingle.
Tempest will have responsibility for Carnival's two UK-based brands, P&O Cruises and Cunard Line.
As part of the restructure at Carnival, commercial director Nigel Esdale, managing director for P&O Cruises Carol Marlow, and president and managing director of Cunard Line Peter Shanks, will now report directly to Tempest, who will oversee all marketing functions. The three previously reported to Dingle.
Dingle said: "Gerard brings with him a very impressive track record and has over 20 years' experience of the hospitality industry in senior commercial and marketing positions, having worked on a number of successful UK and international brands including Marriott and Thistle Hotels. We are delighted to welcome him to Carnival UK."