Matrilineality, at times called matriliny, is the tracing of kinship through the female line. It may also correlate with a social system in which people identify with their matriline, their mother's lineage, and which can involve the inheritance of property and titles. A matriline is a line of descent where a person inherits his or her mother's lineage. In a matrilineal descent system, individuals belong to the same descent group as their mothers. This is in contrast to the currently more popular pattern of patrilineal descent from which a family name is usually derived. The matriline of historical nobility was also called their enatic or uterine ancestry, corresponding to the patrilineal or "agnatic" ancestry.

Scholars disagree on the nature of early human, that is, Homo sapiens, kinship. In the late 19th century, most scholars believed, influenced by Lewis H. Morgan's book Ancient Society, that early kinship was matrilineal. Friedrich Engels took this up in The Origin of the Family, Private Property and the State. This thesis that our first domestic institution was the matrilineal clan, not the family, became communist orthodoxy. However, by the 20th century most social anthropologists disagreed, although during the 1970s and 1980s, feminist scholars often revived it.

In recent years, evolutionary biologists, geneticists and palaeoanthropologists have found indirect genetic and other evidence of early matriliny. Some genetic data suggest that over millennia, female sub-Saharan African hunter-gatherers have lived with their maternal kin after marriage. Also, when sisters and their mothers help each other with childcare, the descent line tends to be matrilineal. Biological anthropologists now largely agree that cooperative childcare helped the large human brain and human psychology to evolve. Most primate species have males dispersing from their birth group and are thus materilinear, though chimpanzees and humans appear to be largely paterilinear.

Matriliny is often tied to matrilocality, which shows significant nuance. Pastoralists and farmers often gravitate toward patrilocality. However, studies show that hunter-gatherer societies have a flexible philopatry or practice multilocality; matrilocality and patrilocality are not the only possibilities. Flexibility leads to a more egalitarian society, as both men and women can choose with whom to live. So, for example, among the pygmy Aka Peoples a young couple usually settles in the husband's camp after the birth of their first child. However, the husband can stay in the wife's community, where one of his brothers or sisters can join him. Kinship and residence in hunter-gatherer societies may thus be complex and multifaceted. Supporting this, a re-check of past data on hunter gatherers showed that about 40% of groups were bilocal, 22.9% matrilocal, and 25% patrilocal.

Matrilineal surnames (matrinames) are names transmitted from mother to daughter, in contrast to the more familiar patrilineal surnames (patrinames) transmitted from father to son, the pattern most common among family names today.

In some societies, membership was—and, in the following list, still is if shown in italics—inherited matrilineally. Examples include many, if not most, Native North American groups: the Cherokee, Choctaw, Gitksan, Haida, Hopi, Iroquois, Lenape, Navajo and Tlingit among others; the Cabécar and Bribri of Costa Rica; the Naso and Guna people of Panama; the Kogi, Wayuu and Carib of South America; the Minangkabau people of West Sumatra, Indonesia and Negeri Sembilan, Malaysia; the Trobrianders, Dobu and Nagovisi of Melanesia; the Nairs, some Thiyyas & Muslims of Kerala and the Mogaveeras, Billavas & the Bunts of Karnataka in south India; the Khasi, Jaintia and Garo of Meghalaya in northeast India and Bangladesh; the Ngalops and Sharchops of Bhutan; the Mosuo of China; the Kayah of Southeast Asia; the Basques of Spain and France; the Akan including the Ashanti, Bono, Akwamu, Fante of Ghana; most groups across the so-called "matrilineal belt" of south-central Africa; the Nubians of Southern Egypt & Sudan; the Tuareg of west and north Africa; and the Serer of Senegal, The Gambia and Mauritania. The title of the Rain Queen in South Africa is inherited via matrilineal primogeniture: dynastic descent is matrilineal, with only females eligible to inherit.

Genetic evidence shows matriliny, and matrilocality, among Celts in Iron Age Britain. As other data indicate patriarchy in the Early Bronze Age, this may indicate a rare patriarchal to matrifocal transition. There is evidence of matrilineal royal descent, from maternal uncle to nephew, in early Iron Age (ca. 500 BCE) Celtics in continental Europe. There is evidence of matriliny in Pre-Islamic Arabia among a subclan of the Amarite tribal confederation of Ancient Saba; the wider society there was overwhelmingly patrilineal. Genetic data has also established matriliny and matrilocality of an elite among Ancestral Pueblo People, from 8th to 11th century AD, in Chaco Canyon, New Mexico. The initial people of Micronesia practiced matrilocality, as seen in ancient DNA. Ancient DNA from a late neolithic site in Northern China (Fujia in Shandong Province), dated around 2700 BCE, showed both matrilocality and possibly a general preference for the maternal bloodline as opposed to affinal (marital) kin.

Matrilineal groups are often made up of matrilineal clans, at times with descent groups or family groups each with a separate female ancestor. Sometimes the male ancestor, that is, the partner of the female ancestor where known, is mentioned as the ancestor though the clan is matrilineal. Surnames in these situations may follow several patterns. The clan name may be the surname, handed down matrilineally. The clan name may be tracked but not used in the personal names. This is true of the Minangkabau, for instance, who mostly use just one name. It is also true of the Akan, who do use two names, but do not inherit the second name, hence making it a surname but not a family name. The surname may also be the name of the descent group.