Sihanouk International Airport — Preah Sihanouk, Cambodia

KOS serves Sihanoukville, a Gulf of Thailand port city named for the former Cambodian monarch Norodom Sihanouk, who championed its development as the country's principal deep-water harbor after independence in the 1950s. For decades a modest beach town popular with backpackers drawn to nearby islands such as Koh Rong, the city transformed abruptly during the 2010s as large-scale Chinese investment poured into casino resorts and high-rise construction, reshaping the coastline and straining local infrastructure in ways that drew considerable domestic debate. The airport itself has seen periods of expanded international service tied to that investment boom, alongside quieter stretches when gaming-related travel slowed following regulatory crackdowns on the industry. Beyond the casino district, Sihanoukville's surrounding coastline still offers beaches, snorkeling, and island-hopping trips that continue to draw independent travelers through KOS. Domestic flights link the airport primarily to Phnom Penh and Siem Reap.