The long jump is a track and field event in which athletes combine speed, strength and agility in an attempt to leap as far as possible from a takeoff point. Along with the triple jump, the two events that measure jumping for distance as a group are referred to as the "horizontal jumps". This event has a history in the ancient Olympic Games and has been a modern Olympic event for men since the first Olympics in 1896 and for women since 1948.

At the elite level, competitors run down a runway (usually coated with the same rubberized surface as running tracks, crumb rubber or vulcanized rubber, known generally as an all-weather track) and jump as far as they can from a wooden or synthetic board, 20 centimetres or eight inches wide, that is built flush with the runway, into a pit filled with soft damp sand. If the competitor starts the leap with any part of the foot past the foul line, the jump is declared a foul and no distance is recorded. To detect this occurrence, a layer of plasticine is placed at a 90° angle immediately after the board. An official (similar to a referee) will also watch the jump and make the determination. In recent times, camera technology and laser sensors have replaced the plasticine at elite competitions (like Diamond League meetings). The competitor can initiate the jump from any point behind the foul line; however, the distance measured will always be perpendicular from the foul line to the nearest break in the sand caused by any part of the body or uniform. Therefore, it is in the best interest of the competitor to get as close to the foul line as possible. Competitors are allowed to place two marks along the side of the runway in order to assist them to jump accurately. At a lesser meet and facilities, the plasticine will likely not exist, the runway might be a different surface or jumpers may initiate their jump from a painted or taped mark on the runway. At a smaller meet, the number of attempts might also be limited to four or three.

Each competitor has a set number of attempts. That would normally be three trials, with three additional jumps being awarded to the best eight or nine (depending on the number of lanes on the track at that facility, so the event is equatable to track events) competitors. All valid attempts will be recorded but only the best mark counts towards the results. The competitor with the longest valid jump (from either the trial or final rounds) is declared the winner at the end of competition. In the event of an exact tie, then comparing the next best jumps of the tied competitors will be used to determine place. In a large, multi-day elite competition (like the Olympics or World Championships), a qualification is held in order to select at least twelve finalists. Ties and automatic qualifying distances are potential factors. The qualification usually takes place in two groups, with each competitor having three attempts. In the final, a set of three trial round jumps will be held, with the best eight performers advancing to the final rounds (attempts four to six). At the 2025 World Championships, the international athletics governing body World Athletics invented a new procedure. After the three trial round jumps in the final, the top ten received an additional fourth attempt, the subsequent top eight a fifth attempt and the subsequent top six a final sixth attempt. (For specific rules and regulations in United States Track & Field see Rule 185)

For record purposes, the maximum accepted wind assistance is two metres per second (4.5 mph).

World Athletics has considered fundamental rule changes to the long jump. In a test phase starting with the 2025 indoor season, athletes will now take off from a wider zone instead of the traditional take-off board. This new 40-centimetre take-off zone was introduced by World Athletics to reduce the number of invalid attempts (around 30%) that have been common in recent years. The international athletics governing body believes that the new take-off zone will not only improve fairness and excitement for the athletes but also provide a more thrilling experience for the audience.

Traditionally, the jump distance is measured perpendicularly from the foul line to the nearest break in the sand. Under the new trial, the measurement will instead be taken from the exact point where the jumper's front foot leaves the zone. Consequently, the effective jump distance is crucial for the outcome of the competition.

During the test phase, the jumps will also be recorded according to the traditional rules and will therefore be eligible for records and top lists.

The long jump is the only known jumping event of ancient Greece's original Olympics' pentathlon events. All events that occurred at the Olympic Games were initially supposed to act as a form of training for warfare. The long jump emerged probably because it mirrored the crossing of obstacles such as streams and ravines. After investigating the surviving depictions of the ancient event it is believed that unlike the modern event, athletes were only allowed a short running start. The athletes carried a weight in each hand, which were called halteres (between 1 and 4.5 kg). These weights were swung forward as the athlete jumped in order to increase momentum. It was commonly believed that the jumper would throw the weights behind him in midair to increase his forward momentum; however, halteres were held throughout the duration of the jump. Swinging them down and back at the end of the jump would change the athlete's center of gravity and allow the athlete to stretch his legs outward, increasing his distance. The jump itself was made from the bater ("that which is trod upon"). It was most likely a simple board placed on the stadium track which was removed after the event. The jumpers would land in what was called a skamma ("dug-up" area). The idea that this was a pit full of sand is wrong. Sand in the jumping pit is a modern invention. The skamma was simply a temporary area dug up for that occasion and not something that remained over time.