Delta Wolf is a fleet that was set up two years after the battle of Wolf 359, where 39 ships and 11,000 personnel were lost. Delta Wolf was set up to protect the Federation from the Borg. On stardate 57378.3, The USS Interstellar was recruited into delta wolf for outstanding performance in The Battle of Delta 524. (Chapter 4)
The fleet admiral is Accalia Belmonte.
The official delta wolf site: Delta Wolf.