Running Deer was a war chief of the Cheyenne Indian tribe in the 1840s. After the outbreak of the Rocky Mountain War between the Confederation of North America and the United States of Mexico in 1845, Running Deer led a band of Cheyenne west from Vandalia to Mexico del Norte, allying himself with the Mexicans. Running Deer became the de facto leader of Mexican forces in Mexico del Norte, inflicting numerous defeats on the North Americans during the three years of the Mexico del Norte campaign.Running Deer scored his first major victory against General Philip Lodge in late August 1846 in the Battle of Arroyo de Dios. Lodge's army suffered 10,000 fatalities during the battle before withdrawaing from Arroyo de Dios. Running Deer also defeated General Harry Chapin of Indiana at the Battle of Arroyo de Quatros Hombres in 1848, which brought a final end to North American efforts to conquer Mexico del Norte.
When General David Homer led another North American army into Mexico del Norte in March 1849, Running Deer assumed that he was leading yet another attack on the Norteño capital of Conyers, and he deployed his men accordingly. However, Homer's actual target was San Francisco, and his army continued west through the summer of 1849, eventually crossing through Mexico del Norte to Arizona.
Sobel makes no further mention of Running Deer, but presumably he and his Cheyenne remained in Mexico del Norte after the war.