Ghislaine Maxwell's Appeal Denied by Supreme Court, 20-Year Sentence Sticks

8:06 AM PT -- Maxwell's attorney David Markus tells TMZ ... “We’re, of course, deeply disappointed that the Supreme Court declined to hear Ghislaine Maxwell’s case. But this fight isn’t over. Serious legal and factual issues remain, and we will continue to pursue every avenue available to ensure that justice is done.”

Ghislaine Maxwell just hit a legal brick wall ... the U.S. Supreme Court flat-out rejected her bid Monday to overturn her conviction for conspiring to sexually abuse minors.

The Supreme Court wasted no time on its first day back with the decision -- killing any shot at a retrial for Maxwell -- who was convicted back in 2021 ... all while the Trump administration continues to catch heat for keeping the Epstein Files still under wraps.

The justices didn’t explain why they turned away the appeal.

Maxwell’s 3 convictions and 20-year sentence stand -- but her lawyer, David Oscar Markus, isn’t throwing in the towel. He says the fight’s far from over... claiming "serious legal and factual issues remain" and vowing to chase every last option to get her justice.

In her appeal, Maxwell argued her conviction should’ve been tossed -- claiming Epstein’s 2007 plea deal covered her, and that prosecutors were way past the statute of limitations.