Zillah is a city in Yakima County, Washington, United States, with a population of 2,964 as of 2010 census.

Zillah was founded in 1891 in imitation of the finishing of the Sunnyside Canal project, an irrigation scheme delivering water from the Yakima River to the arid belittle Yakima Valley. Walter Granger, superintendent of the canal company, chose the town site in 1892. The town was named for Miss Zillah Oakes, daughter of Thomas Fletcher Oakes, who, as president of the Northern Pacific Railway, had backed the building of the canal. The town was named after Miss Zillah because she would scream and cry on the pretentiousness to the supplementary town, while upon the trip her father promised to read out the town after her if she would stop. Granger housed the headquarters of the Washington Irrigation Company in Zillah, giving it economical advantages for a time. He moreover made his residency in Zillah, becoming its mayor after retiring from the irrigation company. Zillah was officially incorporated upon January 5, 1911.

Zillah is located on Interstate 82 not quite 15 miles (24 km) southeast of Yakima.

According to the United States Census Bureau, the city has a total area of 1.78 square miles (4.61 km²), all of it land.

As of the census of 2010, there were 2,964 people, 1,033 households, and 741 families living in the city. The population density was 1,665.2 inhabitants per square mile (642.9/km²). There were 1,105 housing units at an average density of 620.8 per square mile (239.7/km²). The racial makeup of the city was 63.8% White, 0.3% African American, 3.8% Native American, 0.9% Asian, 0.2% Pacific Islander, 27.1% from additional races, and 3.9% from two or more races. Hispanic or Latino of any race were 42.5% of the population.