The Borg are an immensely powerful civilization of cybernetic organisms originated from the Delta Quadrant of the Galaxy. Each Borg is tied up in a sophisticated subspace communications network called the Borg Collective, a shared consciousness in which the idea of the individual is a meaningless concept. Their ultimate goal is to lead all biological life-forms to a higher level of perfection by assimilating them into their collective, i.e. making them all Borg.

First rumors about the Borg came up in the late 23rd century when El-Aurian refugees reported on an attack by a ruthless enemy that devastated their homeworld and abducted or killed almost all of their people. Only few scientists paid attention to them and the only known attempt to contact the Borg was made by the SS Raven, which embarked on an exploration mission in 2350 and never returned.

So first contact with the Borg was not established until 2365, when quasi-omnipotent Q transported the USS Enterprise into the flight path of a Borg vessel located in the Delta Quadrant. Following this incident, Starfleet began advance planning for a potential Borg offensive against the Federation. The anticipated attack came in late 2366, when a Borg vessel entered Federation space, heading for Earth. Starfleet Captain Jean-Luc Picard was captured by the Borg at the beginning of their offensive. He was assimilated into the collective and became known as Locutus of Borg, providing crucial guidance to the Borg in their attack. After a dreadful defeat near Wolf 359, where Starfleet lost 39 ships, the Borg could be eventually stopped in Earth orbit.

The next attack came in 2373, when another Borg vessel invaded Federation space. Again, the Borg were able to break through Federation defenses, this time set up in the Typhoon Sector. Shortly before the vessel was finally destroyed by a Federation fleet, the Borg were able to eject a small escape pod that traveled back in time, trying to rewrite history by preventing Earth's first contact with an alien race. This attempt was thwarted by the crew off the USS Enterprise, who followed the Borg back in time.

The Borg exhibit a high degree of intelligence and adaptability in their tactics. Most means of defense or offense against them were found to work only once, almost immediately after which the Borg developed a countermeasure. Moreover, the Borg's advanced regenerative abilities enable them to repair any suffered damage in a very short time.

The collective is organized by the Borg Queen, who "brings order to the chaos", not as an individual but rather acting as a nexus for the collective Borg mind. All other Borg are drones (analogous to bees), distinguished only by their special tasks. Each Borg has his own designation (such as "3 of 5" or "7 of 9")and belongs to a certain unimatrix. The Queen's hive is located in unimatrix 01.

Borg drones need to return to regeneration cycle for several hours each day where they are supplied with energy. This sleep-like state is spent in an alkoven, a niche with individual energy and data interfaces, specially designed for the drone it belongs to.

There are different types of Borg vessels. The most common one is the Borg cube, a cube-shaped ship with an internal volume of 28 cubic kilometers and a crew complement of 129,000 drones. Smaller ships are the Borg spheres, scout cubes or space probes. The latter have a length of approximately 300m.

Weaponry ranges from tractor beams to laser-like "destruction beams", anti-deflector charges and photon torpedoes. Borg ships are normally protected by a strong magnetic deflector shield. In addition to a normal, high-performance warp drive, their vessels are equipped with transwarp coils, giving them the ability of travelling considerably faster than any Federation ship and reaching the Alpha Quadrant in no more than a few days. All vital systems have several backups, which is why a Borg ship is believed to still work properly after 20% of its volume has been destroyed.