Knott's Berry Farm is a 57-acre (2,500,000 sq ft; 230,000 m²) amusement park in Buena Park, California, United States, owned and operated by Six Flags. In March 2015, it was ranked as the twelfth-most-visited theme park in North America, while averaging approximately 4 million visitors per year. The park features over 40 rides, including roller coasters, family rides, dark rides, and water rides.

Walter and Cordelia Knott first settled in Buena Park in 1920. The park began as a roadside berry stand run by Walter Knott along State Route 39 in California. In 1941, the replica ghost town opened, paving the way for Knott’s Berry Farm to become a theme park. It was officially named Knott’s Berry Farm in 1947. By the 1940s, a restaurant, several shops, and other attractions had been constructed on the property to entertain a growing number of visitors. The site continued its transformation into a modern amusement park over the next two decades, and an admission charge was added in 1968. In 1997, the park was sold to Cedar Fair for $300 million. Cedar Fair later merged with Six Flags in 2024.

The park sits on the site of a former berry farm established by Walter Knott and his family who moved to Buena Park in 1920. Around 1923, the Knott family began selling berries, berry preserves, and pies from a roadside stand called Knott’s Berry Place along State Route 39. In June 1934, the Knotts began selling fried chicken dinners in a tea room on the property, later named "Mrs. Knott's Chicken Dinner Restaurant." The dinners soon became a major tourist draw, and the Knotts built several shops and other attractions to entertain visitors waiting for a seat in the restaurant. In 1940, Walter Knott began constructing a replica Ghost Town on the property, the beginning of the present-day theme park. Ghost Town was Walter Knott's tribute to the pioneers, which included his own grandparents who came to California in a covered wagon from Texas in 1868 (when his mother was two years old). The idea of an amusement park picked up in the 1950s when Walter Knott opened a "summer-long county fair."

Paul von Klieben was Walter Knott's key employee in the creation of the Ghost Town at Knott's Berry Farm and the restoration of the ghost town of Calico, California. In 1941, he joined Knott's as a staff artist, then served as art director there from 1943 to 1953. He traveled to ghost towns in the West, conducted research, and designed most of the Ghost Town section of Knott's Berry Farm. He created concept art for most of the buildings that were built there. He also drew up floor plans, oversaw the construction of buildings, and even spent some time painting concrete to look like natural rock. His Old West paintings and murals adorned the walls of many structures in the park, and a number of them still do. His art was also used extensively in Knott's newspapers, menus, brochures, catalogs and other publications.

In 1956, Walter Knott arranged with Marion Speer to bring his Western Trails Museum collection to Knott's Berry Farm. Speer had been an enthusiastic supporter of Walter Knott's efforts to create Ghost Town, and had written articles for Knott's newspaper, the Ghost Town News. In 1956, twenty years after creating his museum, Marion Speer (at age 72) donated the carefully cataloged collection of 30,000 items to Knott's in return for Knott's housing it, displaying it and naming Speer as curator. Speer continued in that position until he retired in 1969 at the age of 84.

The museum was once housed in a building (which has since been razed) at Knott's Berry Farm between Jeffries Barn (now known as the Wilderness Dance Hall) and the schoolhouse. The Western Trails Museum at Knott's is now just south of the saloon in Ghost Town.

The park became a popular destination for conservative college students in the 1960s, especially as conservative organizations like the California Free Enterprise Association, the Libres Foundation, and the Americanism Educational League were based there. Its conservative appeal was so great that the final rally Barry Goldwater held prior to the 1964 Republican primary election in California, which boasted speakers including Goldwater himself and future president Ronald Reagan, was held at Knott's. According to Assistant Professor Caroline Rolland-Diamond of the Paris West University Nanterre La Défense:

it also appealed to conservative Americans, young and old, because the idealized representation of a past devoid of social and racial tensions that it offered stood in sharp contrast with the political and social upheavals affecting California since the Free Speech Movement erupted at the University of California at Berkeley in 1964.