Biancardi announced the news in a social media post early Wednesday morning ... saying in her native tongue, "This is a private matter."

"But," she continued, "as I am exposed to news, assumptions and jokes on a daily basis, I inform you that I am not in a relationship."

"We are Mavie's parents, and that is the reason for our bond. I hope that this way they will stop relating to the frequent news. Thank you."

The split comes just days after Neymar was accused of sending X-rated messages to a Brazilian OnlyFans model. The soccer superstar, however, denied wrongdoing in the case ... saying on his social media page the leaked DMs were from "years ago."

But, the messages were certainly not the first time the Al-Hilal striker had allegedly been unfaithful toward Bruna -- as he was spotted on camera in a nightclub earlier this year getting close to two women.

Despite the allegations, Neymar and Bruna had seemed to be going strong ... with the two sharing loving pictures together often over the last few months.