NEW YORK — Hotel behemoth Marriott International is becoming even larger, taking over rival chain Starwood in a $12.2 billion deal that will catapult it to become the world’s largest hotelier by a wide margin.

The stock-and-cash deal, if completed, will add 50 percent more rooms to Marriott’s portfolio and give it more unique, design-focused hotels that appeal to younger travelers.

The new company would have 5,500 properties with more than 1.1 million rooms around the world, uniting Starwood’s brands, which include Sheraton, Westin, W and St. Regis, with Marriott’s two dozen brands including Marriott’s Courtyard, Ritz-Carlton and Fairfield Inn.

The deal is expected to close in the middle of 2016.

The next-largest hotel company is Hilton Worldwide with 4,500 properties and about 735,000 rooms.

“To be successful in today’s marketplace, a wide distribution of brands and hotels across price points is critical,” Starwood CEO Adam Aron said on a call with Wall Street analysts. “It appeals to travelers wherever they may go, leverages marketing and technology spend(ing) and strengthens frequent traveler loyalty. Today, size matters.”

Marriott and Starwood — like other hotel chains — own very few individual hotels. Instead they manage or franchise their brands to hundreds of individual owners, often real estate development companies.