Mel Gibson THREATENED his own 78-year-old step-mom ... SPIT IN HER FACE ... and sabotaged her marriage ... this according to legal docs filed by the woman and obtained by TMZ.
Teddy Joye Hicks Gibson -- who married Mel's father Hutton Gibson in 2001 -- has filed for a restraining order against Mel ... claiming he exploded on her several times and now she fears for her safety.
In the docs, Joye claims Mel and his sister Maura hate her guts ... because she doesn't approve of the controversial medical treatments they've been pressuring Hutton to undergo to treat his various ailments.
In the docs, filed by attorney Brian J. Kramer, Joye describes several outbursts in detail:
October 2011 -- Mel screams at Joye because Joye does not approve of "experimental Ozone treatments" Hutton was undergoing for an undisclosed illness.
"Mel began yelling and saying, 'f*ck this and f*ck that' while leveling other extremely offensive language at me."
Joye claims Mel warned her "not to f*ck with [Hutton's] treatments in any way."
January 2012 -- While visiting Hutton in the hospital, Joye claims she said something that set Mel off ... and "Mel got up, looking wild and began yelling at me in a very loud and terrifying voice."
"Mel was so upset and screaming so fiercely that I could see his face turn red."
March 2012 -- Joye, along with Mel and his sister Maura, accompanied Hutton to Panama for stem cell treatment for his hip.
Mel was cooking food and offered some to Joye ... but she declined due to a stomach ache.
Joye claims, "Mel looked at me in disgust and said that I was insulting him by not eating. He then threatened that if I did not eat he would have me put outside."
May 2012 -- During a family meeting to discuss Hutton's health care, "Mel became incensed and began acting like a wild man."
Joye claims Mel began screaming right in her face ... noting, "He was so close that I could feel his spit hitting my face."
She claims Mel's eyes "looked as if they were bulging out of his head."
Joye claims she was paralyzed with fear and later vomited because of the incident.
In the docs, Joye claims Mel and his sister MUST have manipulated their ailing father into filing for divorce ... because Hutton is a devout Catholic and doesn't believe in divorce. Plus, she claims Hutton recently penned her a love note claiming, "Our mutual love is permanent."
Joye claims Mel is even trying to force her out of her home ... because it's owned by a charity that Mel controls. Joye says she has no place else to go.
Joye wants a judge to block Mel from booting her from the home ... and prevent him from interfering with her attempts to communicate with her husband.
She also wants Mel to stay 100 yards away from her at all times.
Moments ago, a California judge decided, rather than issuing a temporary restraining order, to set the matter for a full hearing ... which has been scheduled for next month.
No immediate comment from Mel's rep.