Chris Rock's GF definitely made it look like he's ready to get married again ... to her, but we're told it just ain't so.

Megalyn Echikunwoke and the comedian took a pic where she put her left hand -- and ring finger -- in the spotlight. It was even captioned, "Last night we celebrated new beginnings ... #lovewins."

She had to know that would spark rumors Rock put a ring on it -- but sources close to the couple tell us they're absolutely NOT engaged.

The photo has since been deleted. We're guessing the new beginning was a reference to Chris finalizing his divorce from Malaak.