Omaha kinship is the system of terms and relationships used to define family in Omaha tribal culture. Identified by Lewis Henry Morgan in his 1871 work Systems of Consanguinity and Affinity of the Human Family, the Omaha system is one of the six major kinship systems (Eskimo, Hawaiian, Iroquois, Crow, Omaha, and Sudanese) which he identified internationally.
In this system, relatives are sorted according to their descent and their gender. Ego's father and his brothers are merged and addressed by a single term, and a similar pattern is seen for Ego's mother and her sisters. (Marriages take place among people of different gentes or clans in the tribe.)
Like most other kinship systems, Omaha kinship distinguishes between Parallel and Cross cousins. While Parallel cousins are merged by term and addressed the same as Ego's siblings, Cross cousins are differentiated by generational divisions. On the maternal side, Cross cousins are raised a generation (making them Ego's Mother's Brother and Ego's Mother), while those on the paternal side are lowered a generation (making them the generational equivalent of Ego's Children's).
The system is named for the Omaha, a Native American tribe historically located on the Northern Plains in present-day Nebraska. The Omaha system has been found among some indigenous groups of Mexico, the Mapuche people of Chile and Argentina, the Dani tribe of West Papua, and the Igbo of Nigeria.