Elsie Ann Downey passed at the age of 80 after battling numerous health issues.
"As promotion for The Judge kicks off this weekend, I feel the need to run the risk of over sharing..." RDJ began his Facebook post on Friday. "My mom passed away early this week....I wanna say something about her life, and a generic 'obit' won't suffice..."
In the post, Downey Jr. went on to cover his mother's lackluster acting career and struggle with addiction as well as her bond with him and his children.
"While I strived to have the kind of success that eluded her, my own addiction repeatedly forbade it," Downey Jr. wrote.
"In the summer of 2004, I was in bad shape," the actor continued. "She called me out of the blue, and I admitted everything. I don't remember what she said, but I haven't drank or used since. Eventually, when finances allowed, we were able to move her out to LA. She had a special affinity for my firstborn son Indio, and really got a kick out of Exton. Got an iPad, pictures, videos, the whole 9....
"Her doctors basically titled her a 'Medical Incredible,' said there was little they could do, and were frankly amazed she was up and walking.... Many fond memories of her in the last few years...holidays, kid-stuff, her strutting around with a walking stick. I knew it was difficult, and understood as the visits got shorter.
"She was my role model as an actor, and as a woman who got sober and stayed that way. She was also reclusive, self-deprecating, a stoic Scotch-German rural Pennsylvanian, a ball buster, stubborn, and happy to hold a grudge. My ambition, tenacity, loyalty, 'moods,' grandiosity, occasional passive aggression, and my faith....That's all her...and I wouldn't have it any other way.
"If anyone out there has a mother, and she's not perfect, please call her and say you love her anyway..."