The company announced an agreement with Roark Capital, a US-based group that owns the Baskin-Robbins and Dunkin’ Donuts brands.

The terms of the sale were not disclosed, however Reuters reported that it was valued at more than $9 billion (£7.1 billion).

Subway has expanded fast in recent years despite rising expenses and growing competition.

It praised the acquisition as a “major milestone” that represented the “substantial value of our brand.”

Roark Capital will become one of the world’s largest restaurant operators as a result of the transaction. It already has a stake in the US restaurant conglomerate Inspire Brands, which owns Jimmy John’s, Arby’s, Baskin-Robbins, and Buffalo Wild Wings.

“This transaction reflects Subway’s long-term growth potential, as well as the substantial value of our brand and franchisees around the world,” stated Subway CEO John Chidsey.

In 1965, 17-year-old Fred DeLuca and family friend Peter Buck launched Subway as Pete’s Super Submarines in Bridgeport, Connecticut.

It changed names multiple times before being branded Subway in 1972.

They opened 16 sandwich shops in their native state within two years and then began franchising the brand. It presently has approximately 37,000 locations in over 100 countries.

Franchisees own and run Subway restaurants, which include thousands of entrepreneurs and small business owners.

Roark’s “deep expertise in restaurant and franchise business models” was cited by the company, which stated it had a “bright future” with the private equity group.

It, like many other businesses, has seen increased costs for everything from electricity to food supplies.

However, the business announced in July that global sales climbed 9.8% in the first half of this year compared to the same period in 2022.