Margot Robbie -- PDA ... Public Display of Ass-Grabbin'

"Wolf of Wall Street" star Margot Robbie's boyfriend has his hands full ... of that ass.

Looks like Robbie and aspiring director BF Tom Ackerley want everyone to know they're not only in deep, but they're also not afraid to put the PDA on full throttle .. the two went at it Monday on the streets of Toronto.

No doubt she'll be slipping into something tight for her role as the Joker's squeeze, Harley Quinn, in the upcoming DC Comic bad boy blockbuster, "Suicide Squad" ... which she's up there filming.