Simone Biles is giving the judge who signed Larry Nassar's "death warrant" a big, public thank you ... telling her, "YOU ARE MY HERO" for sentencing the ex-Team USA doc to 175 years in prison.
Simone -- who earlier this month revealed she was sexually assaulted by Nassar -- thanked judge Rosemarie Aquilina in a tweet just hours after Nassar learned his fate in a Michigan courtroom.
In the same message, she also gave a shout-out to all of Nassar's victims who gave impact statements in court "for being so brave and speaking like the queens that you are while looking at that monster."
Biles added -- "He will no longer have the power to steal our happiness or joy. I stand with every one of you."