Richard Dysart Dead -- 'L.A. Law' Star Dies from Cancer at 86

Richard Dysart -- a veteran of stage and screen best known for his role on "L.A. Law" -- died Sunday after a long battle with cancer ... TMZ has learned. He was 86.

According to Dysart's daughter-in-law, he passed away at his home in Santa Monica. His wife tells us he'd been diagnosed with cancer a few years ago.

Dysart had a penchant for playing famous figures -- he portrayed Dwight D. Eisenhower (twice), J. Edgar Hoover (twice) and Harry Truman (twice). He also famously played the villain against Clint Eastwood in "Pale Rider."

But he became a household name as Leland McKenzie on "L.A. Law," which ran from 1986-1994. He was nominated for four Emmys, winning once in 1992.