Washington Court House (often abbreviated as Washington C.H.) is a city in Fayette County, Ohio, United States, and its county seat. The population was 14,401 at the 2020 census. The area was initially settled by Virginia veterans of the American Revolution, who received the land from the government as payment for their service in the war.

Officially named Washington as far back as 1910, the "Court House" suffix was used to distinguish the city from other places in the state with "Washington" in their name (Ohio also has an Old Washington, New Washington, Washingtonville, and Port Washington). The suffix is attributed to settlers who had come from Virginia, where "Court House" was used with county seats (e.g. Appomattox Court House). "Washington C. H." was added to maps and postal guides, and the de facto use of "Washington Court House" persisted over time. The name was made official when the city adopted a new charter in the early 2000s. "Washington Court House" is the longest city name in the state of Ohio.

Washington Court House's first settlers appear to have been Edward Smith Sr., and his family, who emigrated from Pennsylvania in 1810. Smith and his family constructed a crude house in the thick woodlands near Paint Creek, but their efforts to clear the land were interrupted by his departure for military service in the War of 1812. Comparatively soon after returning from his martial pursuits, Smith drowned while attempting to cross a flooded creek, but his widow and 10 children survived and prospered despite the absence of their patriarch. Smith's descendants remained prominent in Fayette County for more than a century after his arrival from Pennsylvania, although many had left Washington Court House for other parts of the county. A family residence still stands on U.S. Route 62 not far outside the city's eastern boundary.

In 1833, Washington Court House (then known as Washington) contained a printing office, seven stores, two taverns, two groceries, a schoolhouse, a meeting house, and about 70 residential houses.

Numerous locations in the city are listed on the National Register of Historic Places. Downtown, the courthouse square has been named a historic district, and a similar designation has been accorded the city cemetery. Nine individual buildings are separately listed on the register: Judy Chapel at the cemetery, the former Washington School, the Fayette County Courthouse, the former William Burnett House (no longer standing), and the Barney Kelley, Jacob Light, Rawlings-Brownell, Robinson-Pavey, and Morris Sharp houses.

Streets within the downtown part of the city around the courthouse building are arranged northeast–southwest and northwest–southeast, rather than east–west and north–south, so that each side of the courthouse receives some sunlight every day of the year.

On October 16, 1894, a crowd gathered outside the Fayette County Courthouse with intent to lynch William "Jasper" Dolby, a black man who had been convicted of sexually assaulting a white woman. Ohio Governor William McKinley called out the militia to subdue the crowd. On October 17, the crowd rushed the courthouse doors and was warned to "disperse or be fired upon." They ignored the warning and continued to batter the doors.

Colonel Alonzo B. Coit ordered his troops to fire through the courthouse doors, killing five men. Colonel Coit was indicted for manslaughter, but was acquitted at trial. After the trial, Governor McKinley stated, "The law was upheld as it should have been... but in this case at fearful cost... Lynching cannot be tolerated in Ohio." The courthouse doors were not repaired or replaced and the bullet holes from the 1894 riot are still present in the southeast doors.