The company closed attractions similar to the roller coaster involved in the incident at Six Flags Over Georgia "out of an abundance of caution", a spokesperson said.
Officials did not confirm how the person died on Monday, nor how the others were injured or their conditions after the incident about 20km northwest of Atlanta.
Detectives with the Cobb County Police Department's major crimes unit are investigating.
A Six Flags spokesperson said the park and local authorities responded immediately and the company was fully co-operating with local authorities.
"We are deeply saddened by the guest incident at our park today," the spokesperson said, adding that they were providing support to the guests and team members impacted.
Authorities and Six Flags did not identify the roller coaster.
However, local TV stations showed video of passengers being evacuated from the Goliath coaster.
The roller coaster, which was opened in 2006, reaches top speeds of about 113km/h and heights of 61 metres, the park's website reports.
During about three-and-a-half minutes, riders "navigate through razor-sharp turns and soar over colossal hills", according to the website.
"I cannot imagine the horror the patrons and employees witnessed today, and my heart aches for the family who lost a loved one," Lisa Cupid, Cobb County Board of Commissioners chairwoman, said in a statement.
She said next of kin had been notified.
The amusement park was a major part of the county's tourism and brings in visitors from across the southeast, Cupid said.
"We are all grappling with how something so devastating could happen at a place that has given generations of families such happy memories," she said.
This death would be at least the seventh at the Georgia park, including one in 2006 in which a man had a likely heart attack on the Goliath coaster, according to the Doan Law Firm, which focuses on amusement park accidents.
It also comes less than two weeks after Six Flags Magic Mountain, in southern California, announced that it was retiring its famous X2 roller coaster amid lawsuits alleging serious brain injury caused by the ride.
The park had settled one wrongful-death lawsuit from the family of a 22-year-old man who died after riding the coaster in 2022.
In 2025, a 32-year-old man died after riding a high-speed roller coaster at the Universal Epic Universe theme park in Florida.
He died from blunt impact injuries and his death was ruled accidental.
