Kings Island was conceived as early as 1964 when Coney Island, a popular amusement park 10 miles (16 km) east of downtown Cincinnati on the banks of the Ohio River, suffered from a major flood that submerged the area in over 14 feet (4.3 m) of water. Although occasional flooding was common at the successful park, the flood in 1964 was the fourth highest on record and caused considerable damage. Faced with already-limited space for expansion and parking, the event triggered discussions within the organization about relocating the park.

Leading the way was Gary Wachs, son of Coney Island president Ralph Wachs, who with friends and family owned a majority of stock. He decided it was time to relocate the park to stay competitive. After years of research and traveling abroad, he presented ideas for a new theme park to the company's board of directors. Some board members opposed relocating, including significant stockholder Charles Sawyer. It was not taken seriously until 1968 when actor Fess Parker announced plans to build a theme park in Northern Kentucky – well within Coney Island's primary market that extended as far south as Louisville. The announcement highlighted the need for change and gave Wachs' proposal credibility within the organization.

Gary and Ralph met with Dudley S. Taft, president of Taft Broadcasting Company, to discuss a possible merger. Taft Broadcasting was interested in promoting its recently acquired Hanna-Barbera division, and in July 1969, the company purchased Coney Island for $6.5 million and 1,600 acres (650 ha) in Warren County, Ohio, for $3.2 million. Kings Island still owned 773 acres (313 ha) of that purchase as of 2005. The site is located between I-71 and the Little Miami River in what was then a part of Deerfield Township. Following the purchase, Fess Parker's efforts to secure financing fell apart along with his plans to build a competing theme park.

Construction began on June 15, 1970. Later that year, a public contest was held to name the new park. "Kings Island" emerged the most popular, as the name was a nod to both the local Kings Mills area as well as the park's predecessor Coney Island. Most of the rides at Coney Island were relocated, and much of what remained was demolished. The popular Sunlite Pool attraction continued to operate, however, and the park was partially restored years later.

Less than two years after breaking ground, Kings Island opened its gates to the public on April 29, 1972. It was the first of several preview events. The grand opening was held the following month on May 27, 1972.

One of the first signature attractions featured at the park was The Racer, a wooden roller coaster consisting of two trains that race side by side on identical tracks. Designed by legendary designer John C. Allen, who was convinced to come out of retirement, The Racer was the first of its kind in 35 years and played an integral part of the roller coaster renaissance of the 1970s. Decades later, it was distinguished as a Roller Coaster Landmark by American Coaster Enthusiasts (ACE) in recognition for its historical significance. Other roller coasters present on opening day in 1972 were the Bavarian Beetle, a small steel coaster brought over from Coney Island, and a new junior wooden coaster in the Happy Land of Hanna-Barbera originally named Scooby Doo. The most expensive ride to open with the park was Enchanted Voyage, a $2-million dark ride attraction that featured over a hundred animatronic Hanna-Barbera characters.

Kings Island was nationally promoted in two well-known sitcoms: The Partridge Family in 1972 and The Brady Bunch in 1973. Each filmed an episode on location at the park, which were later broadcast on ABC. The Brady Bunch was produced by Paramount Television, a large Taft Broadcasting shareholder. The park also held several world-record-breaking events. In 1974, 69-year-old Karl Wallenda set a world record for the longest tightrope skywalk at a distance of 1,800 feet (550 m), which was performed 60 feet (18 m) off the ground. The following year, Evel Knievel successfully jumped fourteen Greyhound buses on his Harley Davidson at Kings Island, clearing a distance of 133 feet (41 m). The jump set a world record that held until 1999. It was the longest successful jump of his career as well as his last major stunt, and the nationally televised event was broadcast live on ABC, landing 52 percent of the TV audience during that hour with an estimated 55 million viewers. Park executives favored the national exposure and additional revenue being generated by record-breaking, newsworthy events that kept the park at the forefront of the industry. To keep momentum going, Kings Island spent years researching and designing a mammoth roller coaster, The Beast, which opened in 1979 as the tallest, fastest, and longest wooden roller coaster in the world. It was designed and manufactured internally by the park.

On the heels of early success came turbulent times beginning in the 1980s. Kings Island partnered with Arrow Development, an amusement ride company well known for its work at Disneyland and Disney World, to develop a unique roller coaster concept. The Bat opened to the public in 1981 as the first modern-day, suspended roller coaster featuring an overhead track with train cars that swung freely from side to side, designed to simulate the feeling of flight. Although it was well received, it was plagued with design flaws and constant maintenance that resulted in frequent closures over its short, three-year history. To appease frustrated guests, the south track of The Racer began running its trains backward in 1982, which became so popular that the change remained until 2008. The park also pushed forward with its next major addition, King Cobra, which opened in 1984 as the first of its kind to be designed from inception as a stand-up roller coaster.

Kings Island also went through a series of ownership changes over the next decade. Taft sold its theme park division in 1984 for $167.5 million to Kings Entertainment Company (KECO), a company formed by senior executives and general managers of Taft Attractions Group. Three parks – Kings Island, Kings Dominion and Carowinds – were involved in the sale. Taft invested in KECO to retain one-third interest. Three years later in 1987, Kings Island was sold individually to American Financial Corporation, led by Carl Lindner. The deal included a contract with KECO to continue managing park operations. KECO, which retained ownership of the other two parks, also added Great America to its portfolio after purchasing it in 1989 from the city of Santa Clara, California.

In 1992 Paramount Communications Inc. (formerly Gulf+Western) purchased KECO along with Kings Island from American Financial in a deal worth $400 million. Paramount formed a new division known as Paramount Parks. KECO owned 20% of Canada's Wonderland, and Paramount bought out the remaining 80% stake in 1993, raising the total number of parks to five. Later that year, Paramount Parks began incorporating themes from its movies into each park. Viacom entered the picture after acquiring Paramount in 1994, paving the way for the inclusion of Nickelodeon themes. Nickelodeon Splat City, an interactive splash pad area, was added in 1995, which later evolved into Nickelodeon Central (2001) and eventually Nickelodeon Universe (2006).

In 1997, a year after leaving Deerfield Township, the city of Mason annexed most of Kings Island. A temporary measure allowed for some land to remain in Deerfield in an attempt to appease park officials and reduce the impact on the township. The rest would be annexed in 1999. In 2005, Viacom split into two companies, Viacom and CBS Corporation, with CBS inheriting Paramount Parks. CBS made the decision to sell its theme park division in January 2006. CBS CEO Leslie Moonves stated that despite the health and profitability of Paramount Parks, the business was "one that just doesn't fit our core strategy".

In 2000 Paramount revealed that they would build a giant record-breaking, 218-foot, looping roller coaster by the name Son of Beast. Son of Beast was built by RCCA (Roller Coaster Corporation of America) who was under qualified to build such a large roller coaster. Halfway through the Son of Beast project, RCCA was fired and Paramount finished the coaster themselves. This led to many problems with the structure and many incidents which eventually led to the coaster being closed in the Cedar Fair era in 2009. The plot of land was replaced with the Son of Beast ghost themed coaster, Banshee.

After receiving interest from several potential suitors, CBS announced the sale of Paramount Parks to Cedar Fair on June 30, 2006, for $1.24 billion. The acquisition of Kings Island gave Cedar Fair, who had recently acquired Geauga Lake from Six Flags in 2004, ownership of all three major amusement parks in Ohio. Part of the agreement allowed Kings Island to continue using Nickelodeon themes and characters for four years and other Paramount-related branding for ten years, with the option to extend the license on both.

Cedar Fair opted for a buyout option within an agreement clause to remove Paramount branding after one season. Beginning in 2008, Face/Off became Invertigo, The Italian Job Stunt Track became Backlot Stunt Coaster, Tomb Raider: The Ride became The Crypt and Top Gun became Flight Deck. Nickelodeon's presence remained until the 2010 season, when Cedar Fair began incorporating its Peanuts theme throughout the park, primarily in the children's area. Nickelodeon Universe was renamed Planet Snoopy to complete the transition.

In late 2009 the Mason City Council added a measure on its 2010 ballot that would mandate a 3-percent ticket tax and a 5-percent parking tax at both Kings Island and The Beach Waterpark. Council member Tony Bradburn argued that it was necessary for the city to help pay for infrastructure improvements, as well as cover police and fire expenses. The proposed tax hike was the center of debate for several months, as Kings Island actively encouraged the public to write, email, and call Mason City Council representatives to express opposition. On February 8, 2010, Mason City Council voted 5–1 against the measure.

A new themed area called Adventure Port was added in 2023, replacing part of Oktoberfest and adding two new family rides – Sol Spin and Cargo Loco. Through the 2024 season, Kings Island expanded Planet Snoopy with the addition of a new themed section called Camp Snoopy.

On July 1, 2024, a merger of equals between Cedar Fair and Six Flags was completed. This merger created Six Flags Entertainment Corporation which encompasses all legacy Six flags and legacy Cedar Fair parks, including Kings Island.