2015–16 Adelaide United FC season

The 2015–16 season was the 12th in the history of Adelaide United Football Club since its establishment in 2003. The club participated in the A-League for the 11th time, the FFA Cup for the second time and the AFC Champions League for the fifth time.

Ahead of the season, manager Josep Gombau stood down, citing family reasons. He was replaced by the club's technical director, Guillermo Amor, in his first senior managerial role. Adelaide United were knocked out of the FFA Cup in the quarter-finals by rivals Melbourne Victory, their first loss in the competition's history. Two and a half weeks later, Adelaide would begin their season by hosting Victory at Adelaide Oval, a match that ended 0–0. The Reds went winless in their first eight games and sat 13 points from the top of the ladder. From round nine onwards, the club went on a 14-match unbeaten run, which saw them sit atop the ladder by the end of it, following a 4–0 win over Wellington Phoenix. A loss to Melbourne City and a draw with the Western Sydney Wanderers put their title charge in doubt. Adelaide won their remaining three matches and thanks to Melbourne Victory's draw with Brisbane Roar in the final round, Adelaide United were premiers by a solitary point.

Adelaide played Melbourne City in the semi-final. After a scoreless first half, Bruce Djite broke the deadlock in the 48th minute, curling the ball into the top right corner from outside the box. Djite would double their lead from the penalty spot 12 minutes later. Fitzgerald pulled a goal back for Melbourne City, but late goals from Dylan McGowan and Pablo Sánchez saw Adelaide into their third Grand Final, which would also be their first time hosting the match. Second-placed Western Sydney Wanderers travelled to Adelaide Oval for the Grand Final. Bruce Kamau scored in the 21st minute and won a free kick that was converted by Isaías in the 32nd minute. Scott Neville's goal just shy of the hour mark brought the Wanderers back into the game, but Adelaide held on, with Pablo Sánchez eventually scoring Adelaide's third to seal the win. This was Adelaide United's first Australian title, and to this day, their last Grand Final they have played in.

Despite the success, Adelaide lost numerous key players ahead of next season, including Bruce Kamau, Pablo Sánchez, Craig Goodwin, Stefan Mauk and Bruce Djite.

Appearances and goals
!colspan="14"|Player(s) transferred out but featured this season