Loch Ness Monster is a steel roller coaster located at Busch Gardens Williamsburg in Williamsburg, Virginia. Manufactured by Arrow Development and designed by Ron Toomer, it was the first roller coaster in the world to feature interlocking loops. The roller coaster was opened within the park's Scottish hamlet, Heatherdowns, on June 2, 1978, and relates to the legend of the Loch Ness Monster. The roller coaster reaches a maximum height of 130 ft (40 m), with a maximum speed of 60 mph (97 km/h), and a total track length of 3,240 ft (990 m).

The Loch Ness Monster is the only remaining roller coaster in the world with interlocking loops. In addition to the interlocking loops, located over one of the park's water features, the design includes a helix tunnel, two lift hills, and a 114.2 ft (34.8 m) drop. Upon opening, the Loch Ness Monster received generally positive reviews. The park has commemorated numerous anniversaries for the Loch Ness Monster and was designated as a Coaster Landmark by American Coaster Enthusiasts.

Busch Gardens: The Old Country theme park in Williamsburg, Virginia, opened in 1975 with one roller coaster, Glissade. With the opening of the park's Oktoberfest section the next year, two roller coasters were added: Das Kätzchen, a children's coaster, and its adult counterpart, Die Wildkatze. As part of its strategy to add an attraction every other year, Anheuser-Busch announced the Loch Ness Monster on July 27, 1977. The thrill ride would be added at Williamsburg Busch Gardens in 1978 and would be the largest ride at the park upon its opening. The ride would be located in the center of the park in the Scotland-themed area and cost around $5 million. The announcement followed expansion plans for the Anheuser-Busch brewery in Williamsburg, as well as similar thrill additions being announced at other theme parks, including its sister park in Tampa, Florida.

Permits for the roller coaster's foundations and several Anheuser-Busch projects were approved in August by the James City County. In anticipation for the new additions, Busch Gardens Williamsburg would increase ticket prices in November. A groundbreaking ceremony was held and construction started in December. Supplemental construction permits were approved by the county in January 1978 for the roller coaster. Construction of the roller coaster was conducted during the winter months, which slowed progress, and was kept relatively hidden to build public anticipation. The Loch Ness Monster was physically revealed to the press on March 2. With the roller coaster nearing completion, the opening date was announced for June. The park's general manager, John Roberts, touted the roller coaster as being the fastest and tallest, and having the steepest drop in the world. The roller coaster would also debut with interlocking loops and a tunnel.

The roller coaster was topped off on April 13, 1978, with final welding, construction of the tunnel, and landscaping to be completed. As part of a marketing ploy, the park searched for eight people to be the first riders to take on the Loch Ness Monster. The eight people represented to take on the roller coaster were athletes in American football, NASCAR racing, ice hockey, and stunt personnel. The Loch Ness Monster opened to the public on June 2. A week later on June 9, the park hosted the inaugural American Coaster Enthusiasts (ACE) convention, partially surrounding the roller coaster's opening. The roller coaster was christened on June 19, by Alex Campbell, an individual claimed to have seen the Loch Ness Monster.

Following a month of rumors in September 2023, Busch Gardens Williamsburg announced the Loch Ness Monster would undertake a renovation for the 2024 season. Throughout the remainder of the 2023 season, sections of the track were replaced while a shade covering was added over the final brake run and various sections of track were repainted. The ride reopened on May 10, 2024 with new audio tracks added to the lift hills and lighting effects in the tunnel, while an all-new sighting center opened April 4-21 as a walkthrough attraction highlighting milestones and archived photographs of the attraction.

The train departs the station and makes a slight left turn. It then makes a sharp right turnaround, passing a boat shack with an old ride vehicle, and starts its climb up the 130 ft (40 m) first lift hill. Cresting the lift hill, the train makes a right turn, and descends 114.2 ft (34.8 m) toward the park's Rhine River at its maximum angle of 55 degrees and reaches its maximum speed of 60 mph (97 km/h). The train climbs a large upward hill and turns left before it briefly ascends, then drops into the first of the two interlocking vertical loops. This loop is followed by a right turn and uphill ascent into the mid-course brake run, followed by a descending, spiraling tunnel. Within the tunnel, the train traverses a helix, making 2.75 rotations. When the train exits the tunnel, it climbs a bunny hill, hits a short brake run, and then climbs a second lift hill. Cresting the hill, the train turns right before descending into the second loop. After completing the loop, the train passes by a statue of the Loch Ness Monster appearing to lunge at riders as it rises up into the final brake run, before returning to the station. One cycle of the ride takes about two minutes and ten seconds to complete.

The roller coaster's namesake comes from the fabled creature of the Loch Ness Monster, appropriately situated in the Scotland area of the park. The queue area of the roller coaster features items of an expedition in search of the Loch Ness Monster. The tunnel portion is labeled the "Monster's Lair", where the Loch Ness Monster lives in a hollowed-out mountain. Special effects were added for the roller coaster's tunnel in 1979, incorporating a mural of the creature with mist and lights. The lighting effect was reintegrated with sound effects in the tunnel section during the 40th anniversary.