The wingspan (or just span) of an airplane is the distance from the left wingtip to the right wingtip. For example, the Boeing 777 has a wingspan of about 60 m (200 feet). Planes with a longer wingspan are generally more efficient because they suffer less induced drag and their wingtip vortices do not affect the wing as much. However, the long wings mean that the plane has a greater moment of inertia about its longitudinal axis and therefore cannot roll as quickly and is less manouverable. Thus, combat aircraft and aerobatic planes usually opt for shorter wingspans to increase manouverability. Since the amount of lift that a wing generates is proportional to the area of the wing, planes with short wings must correspondingly have a longer chord. An aircraft's ratio of its wingspan to chord is therefore very important in determining its characteristics, and aerospace engineers call this value the aspect ratio of a wing.

The term wingspan, more technically extent, is also used for birds, and other winged animals such as pterosaurs, bats, insects, etc. For example, a Wandering Albatross (Diomedea exulans) caught in 1965 had a wingspan of 3.63 m, the official record for a living bird.

To measure the wingspan of a bird, a live or freshly dead specimen is placed flat on its back, the wings are grasped at the wrist joints, and the distance is measured from the tips of the longest primary feathers on each wing.