Recent reports claimed that the musician had proposed to filmmaker Seraphim Ward after five weeks of dating.
Ward herself tweeted a photograph of an engagement ring and said she was "speechless and in shock".
However, Manson's spokesperson has now insisted that his client is not engaged and does not know Ward.
"This is untrue," the representative told Us Weekly. "He has never met this woman."
Manson was previously married to Dita Von Teese until they divorced in 2007. He later dated Evan Rachel Wood but the pair ended their relationship in 2010.
Watch the video for Marilyn Manson's 'No Reflection' below: