Jessica Jaymes -- the porn star best known for becoming Hustler's first contract model to become a member of the AVN Hall of Fame -- has died ... TMZ has learned.

Law enforcement sources tell TMZ ... a friend went to check on Jessica Tuesday afternoon in her San Fernando Valley home because he hadn't heard from her in a while. When the friend arrived at her home, our sources say the friend found Jessica unconscious.

We're told fire and EMS got a call for cardiac arrest for a female. When they got there, nothing seemed amiss. They pronounced her dead at the scene. The cause of death is unknown and now the L.A. County Coroner's Office is investigating.

Jessica had a history of seizures. We're told authorities found various prescription drugs.

Jessica started doing soft porn in 2002 when she was 26. She got her big break in 2004 when Hustler signed her. She made her "coming out" debut in 2005 in the adult film, "The Porn Identity." Jessica snagged Hustler magazine's "Honey of the Year" award that same year.

She went on to appear in well over 200 adult films and was an active performer as of late on her exclusive content website. She also earned some mainstream credits. Jessica appeared as herself on several episodes of the Showtime series "Weeds."

Jessica -- who just last week told her almost 1M Instagram followers she had been on vacation -- also appeared on "The Howard Stern Show," VH1's "Celebrity Rehab Sober House" and HBO's "Vivid Valley."

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Jessica got her stage name combining her real first name and adding the first name of her then-lover, James. She was born Jessica Redding in Anchorage, Alaska. Her mother is of Czech and French descent while her father was reportedly an undercover DEA agent.

She attended New Mexico Military Institute in Roswell, New Mexico before attending and graduating from Rio Salado Community College. She was a fourth through sixth grade teacher for 3 years before becoming an adult film actress. Interesting life.