The Winchester Mystery House is a well-known California mansion that was under construction continuously for 38 years, and is reported to be haunted. It once was the personal residence of Sarah Winchester, the widow of gun magnate William Wirt Winchester, but is now a tourist attraction. Under Winchester's day-to-day guidance, its "from-the-ground-up" construction proceeded around the clock, without interruption, from 1884 until her death on September 5, 1922, at which time work immediately ceased. The cost for such constant building has been estimated at about US $5.5 million (if paid in 1922; this would be equivalent to over $71 million in 2010).

The Queen Anne Style Victorian mansion is renowned for its size and utter lack of any master building plan. According to popular belief, Winchester thought the house was haunted by the ghosts of individuals killed by Winchester rifles, and that only continuous construction would appease them. It is located at 525 South Winchester Blvd. in San Jose, California.