Xôi (Vietnamese pronunciation: [soj˧˧]) is a traditional Vietnamese dish of sticky rice.

With a history tracing back to Tai tribes in Southeast Asia, sticky rice became a staple crop in Vietnam partly due to the region's suitability for its growth. While somewhat replaced by other forms of rice which are easier to grow, it is still eaten in the modern era, prepared in a variety of different ways.

The development process of the customs around xôi is still debated. Although the civilizations of India and China are often thought to be the foundation of modern East and Southeast Asian culture, sticky rice and the customs revolving around it rarely appear in either region. Instead, Southeast Asia has shown the rich development of sticky rice, with each country or ethnic group having unique ways of processing and consuming it.

According to Vietnamese scholars, the customs related to sticky rice have followed the Tai tribes from Yunnan to the Northwestern region of Vietnam from the beginning of the Christian era. This region is still the largest sticky rice growing in Vietnam, partly because this rice variety is only suitable for high terrain with low water. As such, it was known as "the sticky rice zone" (vùng thâm canh lúa nếp). Because of this, sticky rice has become a staple crop in Southeast Asian culture. Over the centuries, xôi – its finished product – has made very rich and diverse developments.

Since ancient times, there has been minimal research to explain the origin of word "xôi" in the Vietnamese languages or at least find a form of intertextuality. According to researcher Trần Quang Đức, the term is the manifestation of a dish made from "gạo nếp" (sticky rice) as almost the only ingredient. In Vietnamese dictionaries, this term is classified as single word, meaning it can be only a noun and not any other form. It should be understood similarly to phở in terms of language function in that the term refers to a processed dish rather than the plant.

Older terms exist for Xôi which are now only used in rural areas, such as "cơm nếp" (Kinh) or "ꪹꪄ꫁ꪱ / khăw-nueng" (Tai), meaning "the meal of sticky rice".

According to The Foundation of Vietnamese Culture (Cơ sở văn hóa Việt Nam, 1995) by Trần Ngọc Thêm, Vietnamese people likely have a long history of using sticky rice (gạo nếp) as a basic daily food. However, it was inherently difficult to grow and often produces unstable yields, so over time, it has been replaced by wet rice (gạo tẻ). Wet rice has gradually become the main staple food because of a few advantages : Good drought tolerance, a harvest of at least two seasons per year (spring and autumn), and nutritional content. In addition, the price of sticky rice is always double the price of wet rice in the agricultural market. This type of rice is often called as "gem rice" (gạo ngọc) or even "heavenly rice" (gạo giời) in Vietnamese folklore. This mainly comes from its round, white and glossy shape, as well as the high nutritional content.

Compared to wet rice, sticky rice has many nutritional advantages, but it proved more difficult to process. First of all, sticky rice must be soaked in pure water (nước sạch) for a night to make its grains bloom bigger, thus ensuring softness after cooking. Before cooking (đồ xôi), sticky rice must be continued to soak with salt water (nước muối). In contrast, the lack of salt will cause the grains of sticky rice to be "thin" (gầy), unable to touch the nerves of the taste buds. Therefore, modern Vietnamese folklore has an extra sentence : "If the bread is indispensable in yeast, how can sticky rice lack salt?". However, after the process of preliminary processing, until sticky rice becomes xôi, its taste remains unchanged. After all, salt acts as solvents, not spices as many people think.