David Harbour gushed Lily Allen has a "stunningly beautiful butt".
The Stranger Things star, 44, admitted his jaw drops when he can't tear his eyes away from his girlfriend's peachy posterior.
Besotted David couldn't resist making the comment about her rounded bottom.
As their headline-grabbing romance continues to heat up, the actor made the cheeky quip in an interview with PEOPLE for their Sexiest Man Alive issue.
He said: "Until she's turned away from me and I stare at her stunningly beautiful butt."
And David revealed the strong sexual attraction he has for her is returned.
The hunk boasted his love said he was "so gorgeous" it was outrageous.
He bragged: "She once told me that I was so gorgeous it was an outrage."
They have gone Instagram official with their budding romance which has been the talk of the celebrity world.
The couple have made no secret of their love for each other as they have been packing on PDA all over New York City.
But they were first seen together in London in August before taking their love to stateside.
Lily has two daughters from her marriage to Sam Cooper.
Her new romance comes after she split from her boyfriend of three years and grime MC Medirian Dan last year.
