Chief Leschi (/ˈlɛʃaɪ/; Lushootseed: ləšx̌iʔ; c. 1808 – February 19, 1858) was a chief of the Nisqually Indian Tribe of southern Puget Sound, Washington, primarily in the area of the Nisqually River.

Following outbreaks of violence and the Yakima Wars (1855–1858), as a leader Leschi was charged with the killings of two Washington Territorial Volunteers. He was hanged for murder on February 19, 1858, although supporters argued that he could not be charged with murder in the death of a combatant in a recognized war. Leschi was informally exonerated in a non-legally binding ruling in 2004 by a Historical Court of Inquiry of Washington State, following a resolution by both houses of the legislature asking the State Supreme Court to vacate his conviction.

Leschi was born in about 1808 into the Mishalpam (″Mashel River people″) or Mica'l Band of Upper (Mountain) Nisqually to a Nisqually chief and a Klickitat (X̣ʷáɬx̣ʷaypam - "Prairie People") woman of the Yakama (Mámachatpam). Their primary village site was Basha'labsh on Mashel River near present La Grande, Washington in what is today southern Pierce County, Washington. He also had an older brother, Quiemuth, and a sister. The Nisqually people (Squalli-Absch - "people of the grass") traditionally occupied a large area along the Nisqually River and its delta at the foot of Puget Sound, an area rich in fish and game. Leschi was respected by his people. The origin of Leschi's name is unknown. Leschi more than likely adopted it, and it may have been influenced by a distant relative, or he may have just enjoyed the sound of it.

Isaac Stevens, first governor of Washington Territory, appointed Leschi as chief in 1854 to represent the Nisqually and Puyallup tribes at the Medicine Creek Treaty council of December 26 of that year. Under pressure, the tribes ceded to the United States all or part of present-day King, Pierce, Lewis, Grays Harbor, Mason, and Thurston counties, agreeing to the requirement that the American Indians inhabiting the area move to reservations.

Some historians say that Leschi either refused to sign (and his "X" was forged by another) or signed under protest. The historical record is unclear on this point. He was reported as arguing that the territory designated as the reservation for the Nisqually tribe was a rocky piece of high ground unsuited to growing food and cut off from access to the Nisqually River, which had provided the salmon that was the mainstay of their diets and culture.

On June 11, 1855, Governor Isaac I. Stevens forced representatives from the Yakima, Nez Perce, Walla Walla, Umatilla and Cayuse tribes to sign a treaty in which the various tribes signed away vast amounts of land in return for money, reservations, and other provisions. Although the treaty stated that white miners would not be allowed on reservation lands, miners frequently passed through these lands, stealing horses from the tribes and abusing Native American women. The Yakima killed some miners in retaliation. When Indian sub-agent, Andrew J. Bolon, tried to investigate the murders, he was killed. Fighting broke out between Major Haller's troops and the Yakima. This conflict marked the start of the Yakima War (1855–56).

Leschi was charged for these murders, in part because of his participation in the Yakima War of 1855–1858. He also was charged for his role in the Battle of Seattle, which took place in January 1856. This battle was of little consequence for the whites, since the natives were held off by the cannons of the Decatur, a naval warship with a crew of about 30. They inflicted little damage on Americans. But Chief Leschi had reportedly been seen commanding the native troops, and was credited with the native attack as a whole. His standing deteriorated among white settlers. Despite this, Stevens was convinced that white settlers were cooperating with Leschi. Stevens declared martial law over Pierce County on April 2, 1856. (Stevens was later charged with contempt of court in relation to this declaration; as governor; however, he pardoned himself.)

On October 30, 1855, seven Washington Territorial Volunteers were attacked by Indians at Connell's Prairie, or Tenalcut Prairie, located between Buckley and Lake Tapps along the White River (in present-day Pierce County). Two were killed, Colonel A. Benton Moses and Joseph Miles. A year later, when hostilities had quieted somewhat, Governor Isaac I. Stevens of Washington Territory, requested that federal troops deliver five Indians for trial. One was Chief Leschi, charged with the murder of Moses. But the federal troops had concluded a peace with Leschi, who had fled east of the Cascades when his war failed. Stevens remained adamant, and the federal troops agreed to find Leschi. They offered fifty blankets for information leading to the arrest and capture of Leschi. Sluggia, a nephew of Leschi, and Eli-ku-kah, a Nisqually, delivered Leschi to the whites. Sluggia had formed a relationship with the chief's youngest wife Mary, which may have added to his zeal to capture Leschi and turn him over to Stevens. Sluggia was later killed by a Leschi loyalist named Wahelut, who was outraged over the nephew's treachery. Wahelnut's fatal shooting of Sluggia was approved by the local tribes.