Vietnam, formally known as the Socialist Republic of Vietnam (SRV), is a nation located on the eastern border of mainland Southeast Asia. With a population of over 100 million, it is the fifteenth most populous country in the world. Its territory is around 331,000 square kilometers (128,000 sq mi). One of Southeast Asia’s two Marxist-Leninist states,[g] Vietnam’s land boundaries are shared with Laos and Cambodia to the west, and China to the north. Through the Gulf of Thailand, it shares marine borders with Thailand; via the South China Sea, it shares borders with the Philippines, Indonesia, and Malaysia. Hanoi serves as the country’s capital, and Ho Chi Minh metropolis, also referred to as Saigon, is its largest metropolis.