The leading edge is a line connecting the forward-most points of a wing's profile. In other words, it's the front edge of the wing. When an aircraft is moving forward, the leading edge is that part of the wing that first contacts the air.Crane, Dale: Dictionary of Aeronautical Terms, third edition, page 305. Aviation Supplies & Academics, 1997. ISBN 1-56027-287-2

During a tailslide, from an aerodynamic point-of-view, the trailing edge becomes the leading edge and vice-versa.

The leading edge may be equipped with one or more of the following:

• leading edge extensions,
• slats,
• slots
• stall strips
• a leading edge cuff
• vortex generators.

The leading edge of a wing can be perpendicular to the airflow, in which case it is called a straight wing. If it meets the airflow at an angle it is referred to as a swept wing. Some aircraft, like the General Dynamics F-111, have moving wings which are referred to as swing wings.

In high-speed aircraft (such as the Space Shuttle), air friction can cause extreme heating of the leading edge. This was the cause of the accident of the Space Shuttle Columbia during re-entry on February 1, 2003. The accident was preceded by a small amount of damage to the RCC tiles on the leading edge, which occurred during take-off.