'Selena' Actress Lupe Ontiveros -- Family Pissed About Oscars 'Memoriam' Snub

The family of "Selena" star Lupe Ontiveros is incredibly upset she was left out of last night's "In Memoriam" presentation at the Oscars ... despite appearing in dozens of major films over the past 30 years.

Ontiveros -- who passed away in July 2012 -- had roles in "Real Women Have Curves", "As Good as it Gets", and "The Goonies" ... but is best known for her role as Yolanda Saldivar, the woman who murdered Selena.

Ontiveros' son Elias tells TMZ ... the whole family gathered to watch the awards show -- and was "disappointed" Lupe wasn't given her proper due -- especially considering some lesser-known people were honored over his mom.

You'll recall, George Clooney did warn some artists might be left out when introducing the tribute, saying, "For for those friends who are on this list tonight, and many others who aren't, we thank you for the memories."

Other celebs snubbed along with Ontiveros -- Andy Griffith, director Gore Vidal, Sherman Hemsley, athlete-turned-actor Alex Karras, and Sylvia Kristel.