The Petún (tobacco in old French), or Tionontati in their [Iroquoian]] language, were an historical First Nations people closely related to the Wendat (Huron) Confederacy. Their homeland was located along the southwest edge of Georgian Bay, in the area immediately to the west of the Huron territory in Southern Ontario of present-day Canada. They had eight to ten villages, and may have numbered several thousand prior to European contact.

Following decimation by infectious disease after 1634, when immigration of children from England, France and Holland increased and brought contact, both the Wendat and Petun societies were in a weakened state. They were attacked, destroyed and dispersed by the Iroquois, raiding from their base in present-day New York in 1649 and French colonial encroachment in the late 17th century. The remnants joined with some refugee Huron to become the Huron-Petun Nation, who were later known as the Wyandot.

French traders called these First Nations people the Petún (tobacco), for their industrious cultivation of that plant. Petun as a word for tobacco became obsolete; it was derived from the early French-Brazilian trade, and comes from the Guarani language. In the Mohawk dialect of the Iroquois, the name for tobacco is O-ye-aug-wa.