The Washington County Fair is an annual event held at the Westside Commons in Hillsboro, Oregon, United States.

The Washington County Fair hosts exhibits of farm animals, food, and flowers along with other type of specialty displays.

Youth members of 4-H and Future Farmers of America participate by showing their animals and specialty collections.

The fair also has an open class for individuals who want to show their livestock, cooking skills, or creative hobbies, but do not belong to an exhibiting organization.

Awards are sponsored by local businesses, civic and service organizations, and individual donors.