I think you are refering to the Battle of Wolf 359. This was the final battle of the first Borg invasion, as depicted in the Star Trek: The Next Generation episode "The Best of Both Worlds" (Part 2) and also re-visited in the Star Trek: Deep Space Nine premiere episode "The Emissary". The battle took place near the star Wolf 359, which is an actual star relatively close to Sol (the sun of the Human homeworld, "Earth", "Terra" or Sol III, located in Sector Zero-zero-one).
During the battle a Borg cube under the command of Locutus (an assimilated Jean-Luc Picard) engaged a fleet of 40 Federation starships. The cube destroyed 39 of those 40 ships before continuing toward Earth.
Starfleet loss of life is numbered at approximately 11,000, as mentioned by retired Admiral Norah Satie in the Star Trek: The Next Generation episode "The Drumhead".
Just an addition to above, in Star Trek: First Contact Picard states that the Borg queen was on the first cube to enter Federation territory. Picard was just the speaker for her, apparently. As well as that, the USS Endeavour (Nebula class) was that one ship that survived Wolf 359, and later assisted the Enterprise in another matter. It was also at the Battle of Sector 001 (Star Trek: First Contact)