Alcohol giant Diageo is buying a fast-growing gin brand co-owned by Ryan Reynolds in a deal worth up to US$610 million.

The company, called Aviation American Gin, is the latest celebrity-backed alcohol brand to be snapped up by Diageo, the world's largest spirits company. Diageo also bought George Clooney's tequila brand, Casamigos, in 2017 for US$700 million, with up to an additional US$300 million based on performance over a decade.

The deal comes at a time when restaurant and bar closures are hurting the sales of Diageo and other big alcohol companies. Diageo's sales for the year ending in June shrank 8.4 per cent.

Diageo's existing gin brands -- which include Tanqueray, Gordon's and Gilbey's -- account for 5 per cent of the company's global net sales and declined by 4 per cent during the year.

Diageo, citing data from alcohol sales-tracking company IWSR, said Aviation American Gin was one of the fastest-growing brands in the super-premium gin category, noting its sales volume doubled in 2019.

Diageo will pay US$335 million upfront for Aviation Gin, then up to US$275 million more based on the company's performance during the next 10 years. Reynolds will maintain an ownership interest in Aviation, Diageo said.

The deal also includes Davos Brands, the spirits company that co-owns Aviation with Reynolds.

Reynolds, whose business interests include ownership in Mint Mobile, acquired a stake in Aviation two years ago.

The "Deadpool" actor known for his deadpan delivery used his comedic chops to elevate the Aviation brand via a series of humorous ads and even a fake Amazon review for the higher-end craft gin.