Kjell Nilsson, who played Lord Humungus in the classic "Mad Max 2" film, has died.

Chris Carbaugh, Kjell's rep, tells TMZ ... the actor died Thursday in Queensland, Australia, surrounded by family after a four-year battle with kidney disease.

The Swedish-born Kjell was an Olympic-class weightlifter ... which came in handy when he was cast as the terrifying, metal-masked Lord Humungus in "Mad Max 2" -- known in America as "The Road Warrior."

Kjell appeared in several other films ... but he was best known for 'Mad Max.'

Chris tells TMZ ... Kjell was a wonderful person who inspired many as a weight-training coach. He loved the 'Mad Max' fans and embraced the role.

He was 76.