Joan Rivers : Remembering Phyllis Diller

Phyllis Diller was way ahead of her time -- so says Joan Rivers, who tells TMZ, Diller didn't get the appreciation she deserved in her prime ... because the 60s sucked for comedy.

Rivers -- whom Diller called her "protegee" -- tells us, "The only tragedy in [Diller's] entire life is that she was funny in an era when you had to look funny to be funny."

Rivers adds, "Her lines were so brilliant that all she had to do was stand on the stage and say 'em and you would have cracked up" ... but in the 60s, Diller's comedy was undermined by stupid outfits.

Rivers says she and Diller were BFFs 'til the end -- in fact, the two grabbed brunch just last month.

Fun fact: Rivers says Diller was dating into her 90s, and even had a boyfriend at the time of her death.

Rivers says Diller "was the most generous of comedians" -- supporting Joan from the very beginning of her career. Rivers adds, "I adored her."

Comedian Phyllis Diller -- who paved the way for today's female comics -- died this morning, TMZ has learned.

Sources close to Diller tell us the comedian died in her sleep at her L.A. home, surrounded by family. She was 95.

We're told Diller had recently fallen, hurting her wrist and hip -- but her rep says the injury had nothing to do with her death.

Diller suffered a heart attack in 1999 and was later fitted with a pacemaker.

Phyllis began her career all the way back in 1952 -- and rose to fame with her TV specials alongside Bob Hope in the 1960.

Later that decade, Phyllis starred in her own show called "The Phyllis Diller Show" ... as well as a variety show called "The Beautiful Phyllis Diller Show." She was also a regular on "Laugh In."

She also posed for Playboy -- but the pics were never published.

Diller remained spunky to the very end, famously appearing in the 2005 movie "The Aristocrats," telling an x-rated joke ... better than comics half her age.

Joan Rivers recently appeared on "Watch What Happens Live" and said, Diller "broke the way for every woman comedian."

Last time we shot Diller was in 2011, and she was still sharp as a tack -- cracking jokes and reminiscing about her "protegee" Joan Rivers. She even named her favorite comedian of all time.