Duane Ollinger, the star of Discovery Channel's "Mystery at Blind Frog Ranch," has died at 68, TMZ has learned.

A family source tells TMZ Duane died yesterday at a Texas hospital following a battle with ALS.

The Texas oilman became a fan favorite on the reality series, which follows Duane and his son Chad as they hunt for a legendary cache of lost Aztec gold believed to be hidden beneath their sprawling Utah property.

The show premiered in 2021 with Duane leading the charge to uncover the treasure he spent years chasing.

Leadership switched to Josh Feldman at the beginning of the sixth season, which kicked off last week -- the move coming after Duane fell ill.

Duane's Blind Frog Ranch became famous for its mysterious underground cave system, local tales of a curse, and his relentless belief that something valuable was buried below.

He was 68.

RIP