Ramona Singer's landed herself into some hot water online ... 'cause she's catching a ton of flak for posting a picture with Daniel Penny -- calling him a "hero."

The former "Real Housewives of New York" star shared the photo to her social media this weekend ... flashing a big smile in a black dress with her arm draped over Penny's shoulder.

Penny's dressed in a suit ... smiling with his own arm wrapped around her back.

Singer captioned the photo, "So proud Daniel Penny !! #apennysaved #hero."

As you can imagine, this didn't go over well with a whole bunch of people on the internet. Many are calling her out for this move -- referring to her as "vile" ... while many others add they saw something like this coming.

Worth noting, there are quite a few conservative voices cheering on Ramona's post ... support for Penny has been split along political lines since he killed Jordan Neely. Singer has since deleted her post.

Remember ... Penny was acquitted on a criminally negligent homicide charge back in December after he placed Neely in what turned out to be a fatal chokehold on a New York City subway back in 2023.

Penny's opponents have claimed he went too far in his actions ... while his supporters have maintained he was just trying to keep his fellow passengers safe.

Penny met with advocates President Donald Trump and Vice President J.D. Vance in December just days after his acquittal ... smiling big at the Army-Navy football game.