Lewiston is a city and the county seat of Nez Perce County, Idaho, United States, in the state's north central region. It is the third-largest city in the northern Idaho region, behind Post Falls and Coeur d'Alene, and the twelfth-largest in the state. Lewiston is the principal city of the Lewiston, ID-WA Metropolitan Statistical Area, which includes all of Nez Perce County and Asotin County, Washington. As of the 2020 census, the population of Lewiston was 34,203, up from 31,894 in 2010.

Lewiston is located at the confluence of the Snake River and Clearwater River, thirty miles (50 km) upstream and southeast of the Lower Granite Dam. Dams and locks on the Snake and Columbia Rivers make Lewiston reachable by some ocean-going vessels. The Port of Lewiston is Idaho's only seaport, and is the farthest inland port linked to the Pacific Ocean. The Lewiston-Nez Perce County Airport serves the city by air.

Lewiston was founded in 1861 in the wake of a gold rush which began the previous year near Pierce, northeast of Lewiston. The city was incorporated by the Washington Territorial Legislature in January 1863. In March 1863, Lewiston became the first capital of the newly created Idaho Territory. Its stint as seat of the new territory's government was short-lived, inasmuch as a resolution to move the capital south to Boise was passed by the Idaho Territorial Legislature on December 7, 1864.

Lewiston's main industries are agriculture, paper, and timber products, and light manufacturing. Ammunition manufacturing maintains a very important and growing presence in Lewiston, being the headquarters of ammunition makers CCI and Speer Bullet. The city is the primary regional transportation, retail, health care, and entertainment center of the surrounding area and serves as a recreation destination for the Hells Canyon National Recreation Area.

Lewiston is home to Lewis–Clark State College, a public undergraduate college. Community events in Lewiston include the Dogwood Festival, Hot August Nights, and the Lewiston Roundup.