The Missouria Tribe (in their own language, Niúachi, also spelled Niutachi) are a Native American tribe that originated in the Great Lakes region of what is now the United States before European contact. The tribe belongs to the Chiwere division of the Siouan language family.
The Missouria migrated west of the Missouri River into Osage territory. During this time, they acquired horses and hunted bison. The French explorer Étienne de Veniard, Sieur de Bourgmont visited the people in the early 1720s. He married the daughter of a Missouria chief. They settled nearby, and Veniard created alliances with the people. He built Fort Orleans in 1723 as a trading post near present-day Brunswick, Missouri. It was occupied until 1726.
In 1730, an attack by the Sauk and Meskwaki tribes nearly destroyed the Missouria, killing hundreds.
In the summer of 1804, the Missouria were one of the first tribes to hold council with Lewis and Clark who were representatives of President Jefferson. The captains presented to the chiefs a document that offered peace while at the same time established the sovereignty of the United States over the tribe.
Some survivors joined with the Otoe, while some joined the Osage and Kansa. After a smallpox outbreak in 1829, fewer than 100 Missouria survived. But some stayed in Missouri.