The Flash: Vertical Velocity, Steel roller coaster at Six Flags Discovery Kingdom, Vallejo, California, US.

The Flash: Vertical Velocity is a steel roller coaster at Six Flags Discovery Kingdom in Vallejo, California, where riders sit in inverted cars that hang below the track. The coaster uses linear induction motors to launch passengers in both directions along a short track at high speed.

The coaster opened in 2001 but its original height exceeded local regulations in Vallejo. The structure was modified in 2002 to meet the city's height limits.

The name references the DC Comics character and connects the ride to a familiar superhero universe that park visitors recognize. This themed attraction sits within the park's broader comic book entertainment zone.

The coaster sits in the DC Comics-themed area of Six Flags Discovery Kingdom, beside Batman: The Ride, Superman: Ultimate Flight and The Joker. Riders board an inverted train of seven cars, two people per row, held by shoulder restraints. The train was removed during the 2016 refurbishment and again went missing after the pandemic closure, and the ride reopened in July 2025 after a 2024 closure.

The coaster has a rollback system that automatically stops and reverses the train if it does not gain enough speed during launch. The front tower has a twisted spiral shape that makes it easy to spot from a distance inside the park.