Star Trek: 10 Times Aliens Influenced Human History
7. Q Introducing The Borg
Q has always had a vested interest in testing and sometimes even protecting humanity. The Next Generation finale All Good Things and the second season of Star Trek: Picard made this incredibly clear.
Because of this, it's reasonable to assume that Q was trying to help humanity by introducing them to the Borg in the Next Generation episode Q Who. He hurled the Enterprise-D to the other side of the galaxy, claiming that he wanted to show them that the Romulans and Klingons were inconsequential compared to the horrors that awaited them in the Delta Quadrant.
Without his interference, Starfleet likely wouldn't have had as much time to prepare for the eventual Borg invasion of Earth, and the Collective could have taken them by surprise and assimilated the planet, then later the entire Federation.
Most of Q's appearances could count as examples of aliens interfering in Human history, but this was probably the most consequential thing he's ever done.