Mobilian Jargon (also Mobilian trade language, Mobilian Trade Jargon, Chickasaw–Choctaw trade language, Yamá) was a pidgin used as a lingua franca among Native American groups living along the Gulf of Mexico around the time of European settlement of the region. It was the main language among Indian tribes in this area, mainly Louisiana. There is evidence indicating its existence as early as the late 17th to early 18th century. The Indian groups that are said to have used it were the Alabama, Apalachee, Biloxi, Chacato, Pakana, Pascagoula, Taensa, Tunica, Caddo, Chickasaw, Houma, Choctaw, Chitimacha, Natchez, and Ofo. The name is thought to refer to the Mobile Indians of the central Gulf Coast, but did not originate from this group; Mobilian Jargon is linguistically and grammatically different from the language traditionally spoken by the Mobile Indians.

Mobilian Jargon facilitated trade between tribes speaking different languages and European settlers. There is continuing debate as to when Mobilian Jargon first began to be spoken. Some scholars, such as James Crawford, have argued that Mobilian Jargon has its origins in the linguistically diverse environment following the establishment of the French colony of Louisiana. Others, however, suggest that the already linguistically diverse environment of the lower Mississippi basin drove the need for a common method of communication prior to regular contact with Europeans.

The Native Americans of the Gulf coast and Mississippi valley have always spoken multiple languages, mainly the languages of the other tribes that inhabited the same area. The Mobilians, like these neighboring tribes, were also multi-lingual. By the early 19th century, Mobilian Jargon evolved from functioning solely as a contact language between people into a means of personal identification. With an increasing presence of outsiders in the Indian Gulf coast community, Mobilian Jargon served as a way of knowing who was truly a native of the area, and allowed Mobilians to be socially isolated from non-Indian population expansion from the north.