Wolf 359

Star Trek: The Next Generation
Episode: TNG 174 - Best of Both Worlds, The, Part I

The star third-closest to Sol and Earth, at about 2.35 parsecs or 7.6 light-years, where some 40 Starfleet ships in Admiral Hanson's armada were routed by the Borg circa stardate 44000. 

They didn't last long enough for expected Klingon aid.