In the 5th season of Bishoujo Senshi Sailor Moon, known as Sailor Moon: Sailor Stars, Sailor Senshi from outside our solar system appear, and our system's senshi become embroiled in the Sailor Wars. Though they are never called "alien senshi" in the series itself, that seems the best way to group them here. The good alien senshi are the Sailor Star Lights:
The evil senshi, under the control of Galaxia
and collectively known as the Anima Mates
I'm including Chibi Chibi
here too, though her true identity wasn't revealed till the last episode.