Question: when do the borg first appear in voyager?
Answer: Voyager. The Borg make frequent appearances in Star Trek: Voyager, which takes place in the Delta Quadrant. The Borg are first seen by Voyager in the third-season episode "Blood Fever" in which Chakotay discovers the body of what the local humanoids refer to as "the Invaders"; which turns out to be the Borg.