The Battle of Wolf 359 is a fictional battle between the combined forces of the Klingon Empire and the United Federation of Planets versus the Borg Collective depicted in the Star Trek: The Next Generation episode "The Best of Both Worlds, Part II" and the Star Trek: Deep Space Nine pilot, "Emissary".
In "The Best of Both Worlds", 40 Starfleet starships and an unknown number of Klingon warships gather near Wolf 359 to intercept a Borg cube ship traveling to Earth. The Borg, having assimilated Captain Jean-Luc Picard and his knowledge of Starfleet tactics and technology into its collective consciousness, obliterate the Starfleet force: according to dialog in "The Drumhead", 39 ships are destroyed, with the loss of over 11,000 lives. Following its victory, the Borg ship continues on its course to Earth, where the crew of the Enterprise-D rescue Picard and stop the cube.
Dialog in "The Drumhead" states that 39 ships were destroyed and 11,000 people died during the battle. Survivors include Benjamin Sisko and his son, Jake, as well as an unknown number of Starfleet and Klingon captives assimiliated by the Borg.
After his rescue, Picard experiences intense guilt because of the thousands whom the Borg killed or injured by using his knowledge. His struggle to cope with his captivity and assimilation is a central element of the episode "Family". Picard's desire for vengeance against the Borg is also an element of the film Star Trek: First Contact.
Benjamin Sisko serves as executive officer aboard the USS Saratoga at the Battle of Wolf 359. His wife, Jennifer, is killed during the battle, and Sisko carries the emotional weight of her death until the end of "Emissary".