In chess, the Wing Gambit is an opening in which White plays an early b4, deflecting an enemy pawn or bishop from c5 so as to regain control of d4, an important central square. Or an opening in which Black plays an early ...b5.
The most common Wing Gambit is in the Sicilian Defence (1.e4 c5 2.b4). The most important Wing Gambit is the Evans Gambit (1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.b4), treated separately.