Mountain Chief (Ninna-stako in the Blackfoot language; c. 1848 – February 2, 1942) was a South Piegan warrior of the Blackfoot Tribe. Mountain Chief was also called Big Brave (Omach-katsi) and adopted the name Frank Mountain Chief. Mountain Chief was involved in the 1870 Marias Massacre, signed the Treaty of Fort Laramie in 1868, and worked with anthropologist Frances Densmore to interpret folksong recordings.