Seven of Nine (full Borg designation: Seven of Nine, Tertiary Adjunct of Unimatrix 01) was a Human female who was a former Borg drone. She was born Annika Hansen on stardate 25479 (2350), and was assimilated by the Borg in 2356 at age six, along with her parents. Liberated by the crew of the USS Voyager in 2374, she joined the crew and returned to the Alpha Quadrant with the starship in 2378.

Annika's parents, Magnus and Erin Hansen, were exobiologists investigating the existence of the Borg. After a great deal of persuasion, the Federation granted the Hansens the use of the USS Raven, a small long range craft, to aid them in their investigation. In 2353, they took Annika, then aged four, along with them. They spent a good deal of time aboard the Raven in search of the Borg; Annika celebrated three birthdays aboard the ship. Eventually, the Hansens encountered a Borg cube and followed it through its transwarp conduit into the Delta Quadrant, the Borg's region of origin. They gathered a great deal of scientific data on the biology of Borg drones and the nature of the Collective by moving undetected through Borg space due to multi-adaptive shielding, invented by Magnus Hansen. They even went aboard Borg vessels, using bio-dampeners to remain undetected. However, their research came to an abrupt end in 2356 when an ion storm struck the Raven. The ship sustained damage, including, most importantly, damage to the multi-adaptive shielding, which went off-line for 13.2 seconds. This left them exposed long enough for the Borg to detect them and perceive them as a target for assimilation. The Hansens tried to evade pursuit by masking the Raven's warp trail, but the Borg still managed to pursue and find them. They and their daughter were promptly captured and assimilated.

"My friends, we have come home." (Star Trek IV: The Voyage Home)