Charlie Sheen to Olbermann -- BACK OFF HOPE SOLO ... She's 'My Gal'

Hope Solo has a Hollywood ally ... Charlie Sheen ... who just warned Keith Olbermann to back off the Team USA soccer star ... and then he asked her out.

Olbermann WENT OFF on Solo this week -- saying she should have (at least) been suspended for the way she berated police officers during her 2014 domestic violence arrest.

But last night, Sheen took to her defense ... saying:

"hey Keith 'Older' man
leave my gal alone.
hey Hope (Han) Solo
After you win the gold
letz hav dinner!
Dutch!"