Louis Gossett Jr.'s Cause of Death Revealed

Louis Gossett Jr. died from a lung condition ... according to his death certificate.

TMZ obtained a copy of the document ... which cites chronic obstructive pulmonary disease (COPD) as the main cause of death. It also notes heart failure and atrial fibrillation as contributing conditions. It says he'd been battling COPD for years.

The death cert also notes Gossett's body was set to be cremated -- and it also lists his occupation as an actor who was working in entertainment.

As we reported ... Gossett -- the first Black man to win the Best Supporting Actor Oscar -- passed away late last month in Santa Monica. At the time, no details about his death were released.

While he received acclaim for his stage roles through the '60s and early '70s, Gossett's breakthrough in Hollywood came in 1977 when he played Fiddler in "Roots" alongside LeVar Burton and John Amos.

His other credits include ... "Watchmen," "Boardwalk Empire," the 'Iron Eagle' film series, "Enemy Mine," "The Deep," and last year's adaptation of the Broadway musical "The Color Purple."

He's survived by two sons Satie -- from his second of three marriages -- and Sharron who he adopted after seeing him on a television segment about at-risk kids.

When we caught up with Louis back in 2021, he told our photog he'd never stop acting despite being 85 years old ... and, he certainly followed through on that vow.

He was 87.