9:39 AM PT -- A Snap spokesperson tells TMZ Sports ... Antonio Brown's account has been suspended and the incident is under investigation.
The platform points out it has strict Community Guidelines that "prohibit sexually explicit content and bullying or harassment of any kind."
8:25 AM PT -- Chelsie Kyriss -- the mother of AB's children -- just released a statement on the situation ... saying she's "very well aware" of the post.
Chelsie says she has repeatedly asked Brown to keep the private parts of their former relationship out of the public eye, but he has refused.