Bethenny Frankel's on-off boyfriend Dennis Shields has died.

The 'Real Housewives of New York' star's former partner - whom she began dating in 2016 - was found dead in his Trump Tower apartment on Friday (10.08.18) at the age of 51, after reportedly suffering from an overdose.

According to TMZ, law enforcement got a call just after 9am for an unresponsive male, and on arrival, they discovered his assistant had administered Narcan - which is used to overturn the effects of an overdose - but was ''unsuccessful in reviving him.''

It has also been reported that the drug Dennis overdosed on was oxycodone, although an autopsy to determine the exact cause of death is still ongoing.

A spokesperson for the New York Police Department told People magazine: ''Preliminarily, we are investigating it as a possible overdose.''

Bethenny first began dating Dennis in 2016, three years after filing for divorce from ex-husband Jason Hoppy, with whom she has seven-year-old daughter Bryn.

The pair endured many break-ups and make-ups - most of which was documented on 'The Real Housewives of New York' - but remained close even when they weren't together.

A source previously said: ''Bethenny and her daughter Bryn love Dennis and his family and they have been a support system during her negative divorce and a positive influence in Bryn's life.

''They had a 27-year friendship before they dated so they picked that up where they left off once they realised they didn't work as a couple. Her daughter adores him and his family, and she comes first above all.''

Bethenny, 47, first met about 28 years ago when he dated and later married one of her high school friends.

As of the time of writing, the Skinnygirl founder has not commented on the news of Dennis' passing.