John-Paul Lipscombe, 53, was a short way into the hike up Mount Rinjani, on Lombok island in the centre of the archipelago, when he collapsed, said local police chief I Wayan Wartia.
“He had walked two kilometres when he suddenly collapsed and died,” he said.
Lipscombe was one of 10 hikers on the trek.
Mount Rinjani, which is 3,726 metres tall, is a popular trekking spot with tourists.
An Italian tourist was killed when she fell into a ravine while climbing the volcano in 2010.