American great Katie Ledecky beat Summer McIntosh to win a thrilling 800-meter freestyle title on Saturday and said her rule for the event is simple: "I don't lose 800s."

Ledecky won her seventh career gold in the event but she was challenged all the way, touching the wall in a championship-record 8 minutes, 5.62 seconds — a fingertip ahead of Australia's Lani Pallister (8:05.98) and McIntosh (8:07.29).

The race was billed as a potential changing of the guard between the 28-year-old Ledecky and McIntosh, a decade her junior and in red-hot form in Singapore.