Mistawasis (Cree: Big Child; born Pierre Belanger) was a Chief of the Sak-kaw-wen-o-wak Plains Cree, notable for his role as the leader of his people during the signing of Treaty 6 in 1876, to which he was the first signatory. Due to the dwindling buffalo population caused by excessive hunting, he was forced to look for new strategies to ensure the survival of his people and their culture. He believed the only way to save his people was to negotiate with the Canadian Government. As a result of his strong influence over the Cree people, he and his close ally Ahtahkakoop were able to argue successfully for the adoption of Treaty 6 by his fellow Cree. After the treaty was signed he remained an ally of the Canadian government until his death.