Galveston police said the teenager was visiting from North Texas.
Officers responded to a single vehicle major accident at the intersection of Spotted Sandpiper Drive and King Rail Circle on the West End of the island around 10 p.m. Sunday.
Witnesses told police a 16-year-old was driving the golf cart westbound on Spotted Sandpiper Drive when she made a sharp turn onto King Rail Circle. The 15-year-old passenger was ejected from the golf cart during the sharp turn, police said.
Upon arrival, officers found the 15-year-old girl lying unconscious with injuries on the roadway.
Galveston EMS transported the teen to UTMB Health Galveston, where she was later pronounced deceased.
The 16-year-old driver was not injured, according to police.
Investigators determined that both girls were not wearing seat belts at the time of the crash.
Police do not believe foul play or intoxication are contributing factors in the accident.
No charges have been filed.