Canadian Prime Minister Justin Trudeau has come under fire for his son's "insensitive" headless Halloween costume ... with followers pointing out how tone-deaf the PM is given the situation in the Middle East.

In snaps shared to Instagram Tuesday, the PM gleefully posed with his nine-year-old son Hadrien, whose head pops out of his black robe to give the illusion of him carrying his own severed head in his hands.

Justin joked about nothing stopping Hadrien from trick-or-treating, even though he "seems to have misplaced something," -- but users on the platform argue it's Justin whose forgotten something -- that a few weeks back, babies and others were beheaded.

Political commentator Tyler Popp labeled Justin's post as "tone-deaf," while Toronto-based Saba Khan, who runs the page @fictionallyflawless, said online that her "heart says this is the most tone deaf thing he can do at a time when children are getting their heads blown off in Palestine."

Others branded Justin's Halloween snaps as "disgusting, insensitive and disrespectful" as well as "mightily inappropriate" and "callousness is beyond belief."

Some folks weren't as disapproving ... criticizing those who turned Hadrien's Halloween costume into something political.

This isn't the first time Justin has come under fire for an insensitive costume. We all remember his apology tour in 2019 when snaps emerged of him sporting a darkened complexion in an Aladdin costume back in 2001.