The Mariposa War (December 1850 – June 1851), also known as the Yosemite Indian War, was a conflict between the United States and the indigenous people of California's Sierra Nevada in the 1850s. The war was fought primarily in Mariposa County and surrounding areas, and was sparked by the discovery of gold in the region. As a result of the military expedition, the Mariposa Battalion became the first non-indigenous group to enter Yosemite Valley and the Nelder Grove.

The war began in 1850 when miners entered the area of the Sierra Nevada foothills, which was traditionally occupied by the Ahwahnechee, a band of the Southern Sierra Miwok people. The miners began to take over the Ahwahnechee's land and resources, leading to tensions between the two groups.

The Ahwahnechee, led by their chief Tenaya, fought back against the miners resulting in a series of skirmishes that escalated into a full-scale war. The California state government, under Governor John McDougall, raised the Mariposa Battalion led by Sheriff James D. Savage to subdue the indigenous people.

The war ended in 1851 with the capture of Tenaya and the surrender of his band. The Ahwahnechee were subsequently removed from the Sierra Nevada foothills and forced to live on reservations. The war resulted in the deaths of an unknown number of Ahwahnechee and several miners, and the displacement of the indigenous people from their ancestral lands.

The Mariposa War was a part of the broader historical context of the California genocide and the American Indian Wars. Many European American settlers considered Native Americans to be an "Indian Problem" which they needed to remove. The United States government, California state government, and White settlers enforced deliberate policies of displacement, forced removals, and massacres that drove Native Americans from their traditional lands and onto reservations.

The California Gold Rush was the conflict that caused the California genocide. By the end of May 1849, more than 40,000 gold seekers had used the California Trail to enter northern and central California which had been up until then populated by Native Americans and Californios (the descendants of early Spanish settlers). In two decades 80 percent of Californias Native American population was wiped out. Many California natives died from their land being seized by white settlers or the diseases brought from the new settlers, and about 9,000 from 16,000 were murdered. In three years, the non-Native American population rose from 14,000 in 1848 to 200,000 in 1852. Immigrants had come from Mexico, South America, Europe, Australia, and China.

Miners digging for gold forced Native Americans off their historic lands. Others were pressed into service in the mines; others had their villages raided by the army and volunteer militia. White settlers also thought it was time to get rid of Native Americans due to the fact they thought took up too much labor in the mines.

Mariposa County Sheriff James Burney and Savage led a militia of seventy four men in a retaliatory attack against a Chowchilla camp on the Fresno River near present-day Oakhurst on January 11, 1851. The militia attacked with rifles at daylight but were surprised when the Chowchilla returned fire with rifles and pistols of their own. Surprised and unprepared, Savage's forces staggered and dispersed, resulting in a victory for the Native Americans who killed several and wounded militia members in what would become known as the first battle of the Mariposa War.