Hainanese chicken rice is a dish of poached chicken and seasoned rice, served with chilli sauce and usually with cucumber garnishes. It was created by immigrants from Hainan in southern China and adapted from the Hainanese dishes of Wenchang chicken and Wenchang chicken rice.

It is widely considered one of the national dishes of Singapore, and is most commonly associated with Singaporean cuisine, being widely available in most food courts and hawker centres around the country. Variants of the dish can also be seen throughout Southeast Asia where Hainanese people settled, particularly in Indonesia, Malaysia, Thailand, and Vietnam, where it remains a culinary staple.

Hainanese chicken rice is a dish adapted from early Chinese immigrants originally from Hainan province in southern China. It is based on a well-known Hainanese dish called Wenchang chicken, which is one of four important Hainan dishes dating to the Qing dynasty. The original dish was adapted by the Hainanese overseas Chinese population in the Nanyang area (present-day Southeast Asia). The Hainanese in China traditionally used a specific breed, the Wenchang chicken, to make the dish. They would usually cook rice with the leftover chicken stock to create a dish known as "Wenchang chicken rice" (文昌鸡饭). Wenchang chicken rice remained a dish for special occasions in Hainanese homes in Singapore until the 1940s.

There is a shared culture of seasoned rice dishes across Hainan and the Leizhou peninsula. Wenchang chicken rice is closely related to another chicken rice dish known as Anpu chicken rice (安铺鸡饭) from Zhanjiang in western Guangdong province, and Anpu chicken rice is speculated to be the predecessor to Wenchang chicken rice. The city of Zhanjiang is also known for its wild betel rice (蛤蒌饭) and duck rice (鸭仔饭).

Almost every country in Asia with a history of immigration from China has a version of Hainanese chicken rice. The San Francisco Chronicle says, "the dish maps 150 years’ immigration from China's Hainan Island...to Singapore and Malaysia, where the dish is often known as Hainan chicken rice; to Vietnam, where it is called "Hai Nam chicken"; and to Thailand, where it has been renamed khao man gai ("chicken fat rice")."

When it comes to the history of Wenchang chicken, according to the records of Lin Zhemin from the Livestock and Veterinary Research Institute of Hainan Province, it has long been a delicacy used by local officials and people to entertain guests. According to the Hainan Chamber of Commerce, it is said that during the Ming Dynasty, a Wenchang native served in the imperial court and brought Wenchang chicken back to his hometown to entertain members of the royal family during the Lunar New Year. As they tasted it, the royals praised, "This chicken hails from the land of culture, where talents gather and the culture flourishes. The chicken is also delicious and fragrant, truly deserving the name Wenchang chicken!"

Additionally, during the reign of the Guangxu Emperor of the Qing Dynasty, there were several large banyan trees in Wenchang, which bore seeds all year round. The chickens pecked at these seeds and became plump and delicious, contributing to the reputation of Wenchang chicken's deliciousness. The earliest mention can be found in the Qing Dynasty book "Lingnan Miscellaneous Poems," which states, "There is a kind of hen in Wenchang County that tastes as good as a rooster."

Based on historical records and inference, Wenchang chicken was introduced to Hainan Island, specifically Wenchang County, around the early 1600s during the Ming Dynasty, along with mainland immigrants, and was cultivated in this unique natural environment. By the Ming and Qing dynasties, there was already a tradition of raising Wenchang chickens in rural areas of Wenchang. It was mainly used as a delicacy for festivals, entertaining guests, and giving gifts. After the revolution in China in 1949, it was still difficult to buy or eat Wenchang chicken in the market or restaurants.