One of the lowest population densities in Asia, at 23 persons per square km, and an estimated population of only 6.2 million people, belies the fact that Laos is home to 68 different ethnic groups.
The peoples of Laos are divided by language, culture, and location. Lao officials distinguish four basic ethnolinguistic groups: the Lao-Lum, or valley Lao; the Lao-Tai, or tribal Tai; the Lao-Theung, better known as the Mon-Khmer; and the Lao-Soung, or Hmong and Man. Mountain people sometimes are called Kha ("Slaves"), a pejorative term.

The Lao-Lum live in the lowlands, on the banks of the Mekong and its tributaries, and in the cities. They speak Laotian Tai, which is closer to the language spoken by the Thai of Thailand than it is to the language of the local Tai-speaking tribes.

The Lao-Tai include such local groups as the Black Tai (Tai Dam) and Red Tai (Tai Deng), both names referring to the dress of the women; the Tai Neua, or Tai of the north; the Tai Phuan of Xiangkhoang province; and the Phu Tai. The Lao-Tai live throughout the country, chiefly in upland areas, and their various dialects are mutually intelligible.

The Lao-Theung (Mon-Khmer) include many groups of people scattered throughout Laos, northeastern Myanmar, northern Thailand, and southern China. They are thought to be descendants of the earliest peoples to inhabit the region. These people do not form a single coherent group but rather include between 25 and 30 distinct groups, some of which are closely related while others are only tenuously identified as being part of this linguistic group.

The Lao-Soung, which include the Hmong (formerly called the Meo, or Miao) and the Man (Yao), are believed to have been coming from southern China since the late 18th century. They are divided into subgroups, and neither constitutes a large proportion of the population of Laos.

Other distinct linguistic groups are few in number. Speakers of Tibeto-Burman dialects, who also came from southern China, live in the north and northwest. Chinese and Vietnamese live primarily in the urban areas. Initially, French was the language of the Lao elite and of the cities, but by the 1970s English had begun to displace it. Under the leadership of the Lao People's Revolutionary Party, Vietnamese has become the third language of the elite.

Prior to the establishment of the Lao People's Democratic Republic (LPDR) in 1975, it was accurate to say that the Lao-Lum peoples had a distinct pattern of culture and dress. They also had a well-defined social structure, differentiating between royalty and commoners. The members of the elite included only a few outsiders who were not descendants of nobility. Most of the elite lived in the cities, drawing their incomes from rural land rents or from urban occupations. After 1975 a new elite emerged representing the victorious leftist forces. Many of this group, however, were of aristocratic origin.

Traditionally, Lao-Tai society had a stratified social structure and a political hierarchy. The people were organized into groups larger than villages called muong, each of which was ruled by a hereditary ruler called the chao muong. Within this broad grouping, however, there were ethnic variations. Among the Black Tai, the nobility consisted of two descent groups, the Lo and the Cam, who provided the rulers of the muong. The religious leaders came from two other descent groups, the Luong and the Ka. The Black Tai tribal organization had three levels: the village; the commune, which was composed of a number of villages; and the overall muong. The latter two were ruled by nobles, while the village headman was selected from among the commoners by the heads of households. The Red Tai had a similar social structure, with the addition of a council of five to aid the chao muong. The nobility owned the land and had the right of service from the commoners.

The Mon-Khmer had no political or social structure beyond the village. They were led by a village headman, who was their link to the central government; but his role in the village was not clear.

Among the Lao-Soung, the Hmong maintained the tradition of a king and subchiefs and a large-scale organization, although in practice this usually was limited to the village. The village consisted of several extended families. In some villages, all the heads of households were members of a single clan, and the head of the clan was the headman of the village. Where several clans resided together in a large village there were several headmen, one being the nominal head and the link to the government. The headman had real authority in the village and was aided by a council. The Hmong extended their organization beyond the village for military purposes.