Chaos at a Minnesota town hall where Rep. Ilhan Omar was speaking … a man rushed up to the podium and squirted her with an unknown substance … and it’s all on video.

The Congresswoman was meeting in her Minneapolis district Tuesday for her first town hall since Border Patrol agents shot and killed Alex Pretti when she was approached by the liquid-spraying maniac.

Omar had just called on Department of Homeland Security Secretary Kristi Noem to resign when the man leapt out of his seat and charged at her … squirting her top with an unknown, liquid substance.

Unclear what Omar got sprayed with here, but she kept on speaking after things calmed down.