Le surf (abréviation de l'anglais surf-riding, surf = ressac et to ride = chevaucher) est un sport qui consiste à glisser sur les vagues, ondes de surface, au bord de l'océan, debout sur une planche. Le surf se pratique sur des sites de surf, appelés "spots", des plages propices au surf qui sont baignées par des vagues plus ou moins grandes. Les adeptes de ce sport sont les surfeurs (ou les aquaplanchistes).

Historique
La plupart des experts et sources s'accordent à penser que le surf trouverait ses origines à Hawaï. Un surf similaire à celui pratiqué aujourd'hui est décrit par des sources européennes telles que le capitaine James Cook, il y a plus de 300 ans (1778: découverte des îles Hawaï par James Cook).

La plus ancienne planche de surf connue à ce jour a été découverte en 1905 à Ko'Okena, sur la grande île d'Hawaii, à l'intérieur d'un tombeau. Les archéologues pensent qu'il s'agissait de la sépulture d'une "cheffesse" nommée Kaneamuna, qui régnait au début du XIVe siècle. Fabriquée dans le fond de l'arbre à pain, cette planche fut retrouvée en parfait état de conservation.

Le surf a pendant longtemps été une partie intégrante de la culture hawaïenne: les premiers compte-rendus à ce sujets seraient ceux de Samuel Wallis et de l'équipage du Dauphin, premiers Européens à mettre le pied à Tahiti en 1767, ou Joseph Banks, botaniste embarqué sur le HMS Endeavour de Cook et arriva sur la même île en 1769. Le Lieutenant James King, en fera mention en complétant les mémoires de Cook après le décès de celui-ci en 1779. En 1788, James Morrison, un des mutins de la Bounty, décrit de manière similaire la pratique du hōrue à Tahiti.

Quand Mark Twain visite Hawaii en 1866, il décrit des "indigènes, de tous sexes et ages, s'amusant avec ce passe-temps national qu'est le surf".

Les longboards (ou planches longues) sont les descendants modernes des premières planches apparues et descendent d'une longue tradition hawaiienne. Les shortboards (ou planches courtes) sont apparues dans les années 1960-1970. Plus légères, plus relevéees et effilées au niveau du nez, plus fines, elles sont beaucoup plus maniables et offrent une liberté beaucoup plus importante au surfeur dans sa trajectoire et les figures qu'il peut réaliser.
 
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Surfing is a surface water sport in which the wave rider, referred to as a surfer, rides on the forward or deep face of a moving wave, which is usually carrying the surfer toward the shore. Waves suitable for surfing are primarily found in the ocean, but can also be found in lakes or in rivers in the form of a standing wave or tidal bore. However, surfers can also utilize artificial waves such as those from boat wakes and the waves created in artificial wave pools.

The term surfing refers to the act of riding a wave, regardless of whether the wave is ridden with a board or without a board, and regardless of the stance used (goofy or regular stance). The native peoples of the Pacific, for instance, surfed waves on alaia, paipo, and other such craft, and did so on their belly and knees. The modern-day definition of surfing, however, most often refers to a surfer riding a wave standing up on a surfboard; this is also referred to as stand-up surfing.

One variety of stand-up surfing is paddle boarding. Another prominent form of surfing is body boarding, when a surfer rides a wave on a bodyboard, either lying on their belly, drop knee, or sometimes even standing up on a body board. Other types of surfing include knee boarding, surf matting (riding inflatable mats), and using foils. Body surfing, where the wave is surfed without a board, using the surfer's own body to catch and ride the wave, is very common and is considered by some to be the purest form of surfing.

Three major subdivisions within standing-up surfing are long boarding, short boarding, and stand up paddle surfing (SUP), and these three have several major differences, including the board design and length, the riding style, and the kind of wave that is ridden.

In tow-in surfing (most often, but not exclusively, associated with big wave surfing), a motorized water vehicle, such as a personal watercraft, tows the surfer into the wave front, helping the surfer match a large wave's speed, which is generally a higher speed than a self-propelled surfer can produce. Surfing-related sports such as paddle boarding and sea kayaking do not require waves, and other derivative sports such as kite surfing and windsurfing rely primarily on wind for power, yet all of these platforms may also be used to ride waves. Recently with the use of V-drive boats, Wakesurfing, in which one surfs on the wake of a boat, has emerged. The Guinness Book of World Records recognized a 78 feet (23.8 m) wave ride by Garrett McNamara at Nazaré, Portugal as the largest wave ever surfed, although this remains an issue of much contention amongst many surfers, given the difficulty of measuring a constantly changing mound of water.

Origins and history
For centuries, surfing was a central part of ancient Polynesian culture. Surfing may have first been observed by Europeans at Tahiti in 1767 by Samuel Wallis and the crew members of the Dolphin who were the first Europeans to visit the island in June of that year. Another candidate is the botanist Joseph Banks being part of the first voyage of James Cook on the HMS Endeavour, who arrived on Tahiti on 10 April 1769. Lieutenant James King was the first person to write about the art of surfing on Hawaii when he was completing the journals of Captain James Cook upon Cook's death in 1779.

When Mark Twain visited Hawaii in 1866 he wrote : - "In one place we came upon a large company of naked natives, of both sexes and all ages, amusing themselves with the national pastime of surf-bathing".

References to surf riding on planks and single canoe hulls are also verified for pre-contact Samoa, where surfing was called fa'ase'e or se'egalu (see Augustin Krämer, The Samoa Islands) and Tonga far pre-dating the practice of surfing by Hawaiians and eastern Polynesians by over a thousand years.

In July 1885, three teenage Hawaiian princes took a break from their boarding school, St. Mathew’s Hall in San Mateo, and came to cool off in Santa Cruz, California. There, David Kawananakoa, Edward Keliiahonui and Jonah Kuhio Kalaniana'ole surfed the mouth of the San Lorenzo River on custom-shaped redwood boards, according to surf historians Kim Stoner and Geoff Dunn.

George Freeth (8 November 1883 – 7 April 1919) is often credited as being the "Father of Modern Surfing". He is thought to have been the first modern surfer.

In 1907, the eclectic interests of the land baron Henry Huntington brought the ancient art of surfing to the California coast. While on vacation, Huntington had seen Hawaiian boys surfing the island waves. Looking for a way to entice visitors to the area of Redondo Beach, where he had heavily invested in real estate, he hired a young Hawaiian to ride surfboards. George Freeth decided to revive the art of surfing, but had little success with the huge 16-foot hardwood boards that were popular at that time. When he cut them in half to make them more manageable, he created the original "Long board", which made him the talk of the islands. To the delight of visitors, Freeth exhibited his surfing skills twice a day in front of the Hotel Redondo.

In 1975, professional contests started. That year Margo Oberg became the first female professional surfer.