The holding company award is based on the total number of points won by each group’s agencies during the week of the festival.
Agencies from nearly 50 countries contributed points to help secure WPP Group's Lions victory over rivals Omnicom, Publicis Groupe, Dentsu Aegis Network and IPG, for the fourth consecutive year.
Among WPP's notable winners was advertising network Ogilvy & Mather, crowned network of the year for the third year in a row.
Other examples of winning work from WPP agencies included OgilvyOne London’s "Magic of Flying" for BA picking up Media and Cyber Lions awards.
Sorrell, chief executive of WPP, said: "We normally describe Cannes as our Oscars but this year it’s the World Cup of advertising and marketing. We’re thrilled to lift it for the fourth year in a row."
WPP's victory follows a year in which the group's two biggest rivals - Omnicom and Publicis Groupe - announced, and later scrapped, plans to merge and create the biggest holding group in the world.
Winning the award tonight, Sorrell was unable to resist hinting at the failed merger, which earlier this week he had blamed on "a clash of egos and lack of planning".
He said: "Over the last 12 months there have been a few distractions for some in the industry, so it’s good to focus on the core of our business: brilliant work for clients. Huge thanks and congratulations to all our winning people, agencies and networks."
John O’Keeffe, worldwide creative director of WPP, was more magnanimous, adding: "A tough contest has come to a gratifying conclusion for WPP here in Cannes.
"The closeness of the result is testament not only to our own strength, but that of our competitors as well, who I know will be just as hard to beat next year. Congratulations to everyone whose work has made Cannes 2014 such an amazing showcase for our industry."
Other WPP award winners in Cannes 2014 included: Ogilvy & Mather Brazil’s "Bald Cartoons" for GRAACC, the children’s cancer institute; "Unload your 401k" by Grey New York; "Turning Packaging into Education" from Y&R Yangon/Red Fuse for Colgate Palmolive, bringing Myanmar its first ever Lion; Ogilvy South Africa’s "Give Me Strength" for Lucozade; "The Autocomplete Truth" for UN Women by Memac Ogilvy; Y&R Beijing’s campaign for Penguin China; and Bob Dylan’s "Like a Rolling Stone" box set release by Interlude New York for Sony Music.