Lacey is a city in Thurston County, Washington, United States. It is a suburb of Olympia subsequently a population of 42,393 at the 2010 census. Lacey is located along Interstate 5 with Olympia and the Nisqually River, which marks the attach with Pierce County and Joint Base Lewis–McChord.

Lacey was originally called Woodland after settlers Isaac and Catherine Wood, who claimed home there in 1853. By 1891, the town of Woodland had a large satisfactory population to apply for a name office. The demand was denied because there was already a town called Woodland on the Columbia River. The broadcast Lacey was agreed for the other post office application, presumably after O. C. Lacey, the local Justice of the Peace. The small settlements of Woodland and Chambers Prairie consolidated into Lacey in the 1950s. The city of Lacey was not officially incorporated until 1966. At the time, the main industries were cattle, milk, forest products, and retail. Lacey became a commuter town for Olympia, Fort Lewis and to some extent, Tacoma; in recent years, however, business developments, community groups, and population layer have led Lacey to build into a city in its own right.

According to the United States Census Bureau, the city has a total Place of 16.51 square miles (42.76 km²), of which, 16.06 square miles (41.60 km²) is estate and 0.45 square miles (1.17 km²) is water.

As of 2000 the median pension for a household in the city was $46,848, and the median pension for a relatives was $54,923. Males had a median income of $41,053 versus $32,497 for females. The per capita pension for the city was $20,224. About 7.1% of families and 8.8% of the population were below the poverty line, including 10.5% of those below age 18 and 5.5% of those age 65 or over.

As of the census of 2010, there were 42,393 people, 16,949 households, and 10,869 families residing in the city. The population density was 2,639.7 inhabitants per square mile (1,019.2/km²). There were 18,493 housing units at an average density of 1,151.5 per square mile (444.6/km²). The racial makeup of the city was 74.2% White, 5.4% African American, 1.2% Native American, 8.0% Asian, 1.7% Pacific Islander, 2.6% from extra races, and 7.0% from two or more races. Hispanic or Latino of any race were 9.2% of the population.