He replaces Philip Almond who left the role in August to become global marketing director for Baileys.
Gladman, who is based in the US, has been with Diageo for more than nine years. Prior to his current role, he led the European innovation agenda introducing brands such as Baileys Flavours and Guinness Surger.
Before joining Diageo, he worked at Procter & Gamble where he was global brand manager for Max Factor.
In his new role, which takes effect from June, Gladman will be responsible for the brand, category and responsible drinking marketing agenda for Diageo GB.
He will report to Diageo GB managing director, Simon Litherland.