Teenager Missy Franklin powered past Australia's Alicia Coutts on the final leg at the Palau Sant Jordi to lead the U.S. team home in a time of seven minutes 45.14 seconds.
Australia took silver in 7:47.08 and France, who led at the halfway stage, bronze in 7:48.43.
The U.S. triumph, adding to their victory in Sunday's 4x100 freestyle relay, brought a fourth gold of the week for Franklin and a third for Katie Ledecky.
The result was the same as the 4x200 freestyle final at the Olympic Games in London last year.
- Sports & Recreation
- Missy Franklin
- Alicia Coutts