Morgan Freeman paid tribute to Gene Hackman during the Oscars on Sunday ... remembering Gene as an actor who elevated everyone else's work -- and won the hearts of film lovers of all over the world.

The veteran actor came onstage before the in memoriam section kicked off to talk about his costar who passed away last week.

Freeman mentions the the two movies he and Gene worked on together -- "Unforgiven" and "Under Suspicion" ... and said Gene helped elevate the work of the entire cast and crew on both sets.

While Morgan mentions that Gene won two Academy Awards -- he adds that Gene's real accomplishment was winning the love of film buffs everywhere.

MF says GH didn't want to be remembered for his movies ... but simply as someone who always tried to do good work -- a mark he definitely hit, Freeman says.

We broke the story ... revealing Freeman was expected to speak about his longtime friend at the ceremony just days after Gene and his wife Betsy Awakawa were found dead in their home.

Cops labeled their deaths "suspicious" -- leading to a search of the house during which they took pills, a calendar and health records.

In a news conference Friday, Santa Fe County Sheriff Adan Mendoza said it appears Gene's pacemaker had its last event on February 17 ... indicating that's when he passed away. He was found more than a week later on February 26.

Gene was 95 ... Betsy was 65.

RIP