Final answer:
The biggest hotel chain in the world by rooms is Marriott International, with over 1 million rooms across various brands and property types.
Step-by-step explanation:
The biggest hotel chain in the world by the number of rooms is Marriott International. As of my knowledge cutoff in 2023, Marriott operates a mix of company-owned and franchised properties with a total room count well over 1 million.
This includes a variety of different brands under their umbrella, ranging from budget-friendly options to luxury accommodations. The scale and reach of Marriott International demonstrate the company's significant impact on the global hospitality industry.