Lilliwaup is a small unincorporated community in Mason County, Washington, United States.
The area was settled by early pioneers by 1854. The town was officially platted in 1890. The Olympic Exploring Expedition of 1890, led by Joseph O'Neil, made one of the earliest explorations of the Olympic Mountains and the first crossing of the southern part of the range. The expedition began at Lilliwaup. O'Neil hoped to find a practical route between Hood Canal and the Pacific Ocean.When O'Neil's exploring expedition first arrived at Lilliwaup in early 1890 they found the town almost non-existent. A member of the party described Lilliwaup as "a town with one house". But in September of the same year, when O'Neil again traveled to Lake Cushman via Lilliwaup more than 30 families had moved in. Soon after there was a store and two hotels. By the 1920s tourism was bringing new life to the region.