The First Lady got an earful from the crowd when she was introduced Tuesday at the B'More Youth Summit, and the boos continued during her speech addressing the nation's opioid crisis.

The Trumps have a pretty strained relationship with Baltimore, to put it lightly.

You'll recall ... President Trump ripped the city back in July, referring to the late Rep. Elijah Cummings' district, which includes parts of Baltimore, as a "disgusting, rat and rodent infested mess" and a "very dangerous and filthy place."

The boo birds stuck around after the initial salvo ... Melania was again booed -- and cheered -- as she left the stage after giving her remarks.

We've seen the Prez booed at sporting events recently -- at the World Series in D.C. and UFC 244 in NYC -- but this is the first time Melania has been booed publicly during a solo appearance.