The America's Cup is a is the oldest international competition still operating in any sport.

The cup was originally known as the 'R.Y.S. £100 Cup', awarded in 1851 by the British Royal Yacht Squadron for a race around the Isle of Wight in the United Kingdom. The winning yacht was a schooner called America, owned by a syndicate of members from the New York Yacht Club (NYYC). In 1857, the syndicate permanently donated the trophy to the NYYC, under a Deed of Gift that renamed the trophy as the 'America's Cup' after the first winner and required it be made available for perpetual international competition.

From the first defence of the cup in 1870 until the twentieth defence in 1967, there was always only one challenger. In 1970 multiple challengers applied, so a selection series was held to decide which applicant would become the official challenger and compete in the America's Cup match. This approach has been used for each subsequent competition. The trophy was held by the NYYC from 1857 until 1983. The NYYC successfully defended the trophy twenty-four times in a row before being defeated by the Royal Perth Yacht Club, represented by the yacht Australia II. Including the original 1851 victory, the NYYC's 132-year reign was the longest (in terms of time) winning streak in any sport.

Early matches for the cup were raced between yachts on the waterline owned by wealthy sportsmen. This culminated with the J-Class regattas of the 1930s. After World War II and almost twenty years without a challenge, the NYYC made changes to the deed of gift to allow smaller, less expensive 12-metre class yachts to compete; this class was used from 1958 until 1987. It was replaced in 1990 by the International America's Cup Class, which was used until 2007. After a long legal battle, the 2010 America's Cup was raced in waterline multihull yachts in Valencia, Spain. The victorious Golden Gate Yacht Club then elected to race the 2013 America's Cup in AC72 foiling, wing-sail catamarans and successfully defended the cup. The 2017 America's Cup match was sailed in foiling catamarans, after legal battles and disputes over the rule changes."America’s Cup boat size row escalates as teams close ranks after Luna Rossa exit" , The Guardian, 3 April 2015

Origins The America's Cup is the oldest competition in international sport, and the fourth oldest continuous sporting trophy of any kind. The cup itself was manufactured in 1848 and first called the "RYS £100 Cup". It was first raced for on 22 August 1851 around the Isle of Wight off Southampton and Portsmouth in Hampshire, England, in a fleet race between the New York Yacht Club's America and 15 yachts of the Royal Yacht Squadron. The race was witnessed by Queen Victoria and the future Edward VII and won by America. This is considered to be the first America's Cup race.

On 8 July 1857, the surviving members of the America syndicate donated the cup to the New York Yacht Club via the Deed of Gift of the America's Cup filed with the New York Supreme Court. The deed is the primary instrument that governs the rules to make a valid challenge for the America's Cup and the rules of conduct of the races. It states that the cup "is donated upon the condition that it shall be preserved as a perpetual challenge Cup for friendly competition between foreign countries", outlines how a foreign yacht club can make a challenge to the holder of the cup and what happens if they do not agree on how the match should be conducted. The deed makes it "distinctly understood that the cup is to be the property of the club [that has most recently won a match for the cup], subject to the provisions of this deed, and not the property of the owner or owners of any vessel winning a match".

1851: America wins the Cup

In 1851 Commodore John Cox Stevens, a charter member of the fledgling New York Yacht Club (NYYC), formed a six-person syndicate to build a yacht with intention of taking her to England and making some money competing in yachting regattas and match races. The syndicate contracted with pilot boat designer George Steers for a schooner, which was christened America and launched on 3 May 1851.

On 22 August 1851, America raced against 15 yachts of the Royal Yacht Squadron in the club's annual regatta around the Isle of Wight. America won, finishing 8 minutes ahead of the closest rival. Apocryphally, Queen Victoria, who was watching at the finish line, was reported to have asked who was second, the famous answer being: "Ah, Your Majesty, there is no second."

The surviving members of the America syndicate donated the cup via the Deed of Gift of the America's Cup to the NYYC on 8 July 1857, specifying that it be held in trust as a perpetual challenge trophy to promote friendly competition among nations.

1870–1881: First challenges

No challenge to race for the Cup was issued until British railway tycoon James Lloyd Ashbury's topsail schooner Cambria (188 tons, 1868 design) beat the Yankee schooner Sappho (274.4 tons, 1867 design) in the Solent in 1868. This success encouraged the Royal Thames Yacht Club in believing that the cup could be brought back home, and officially placed the first challenge in 1870. Ashbury entered Cambria in the NYYC Queen's Cup race in New York City on 8 August against a fleet of seventeen schooners, with time allowed based on their tonnage. The Cambria only placed eighth, behind the aging America (178.6 tons, 1851) in fourth place and Franklin Osgood's Magic (92.2 tons, 1857) in the fleet's lead.

Trying again, Ashbury offered a best-of-seven match race challenge for October 1871, which the NYYC accepted provided a defending yacht could be chosen on the morning of each race. Ashbury's new yacht Livonia (264 tons) was beaten twice in a row by Osgood's new centreboard schooner Columbia (220 tons), which withdrew in the third race after dismasting. The yacht Sappho then stepped in as defender to win the fourth and fifth races, thereby successfully defending the cup. Although the event ended in acrimony, Ashbury was the catalyst for the introduction of greater fairness in no longer allowing the defender to use multiple yachts against a single challenger.

The next challenge, in 1876 from the Royal Canadian Yacht Club, was the first to be disputed between two yachts only. The schooner Madeleine (148.2 tons, 1868), a previous defender from the 1870 fleet race, easily defeated the challenger Countess of Dufferin (221 tons, 1876 design by Alexander Cuthbert). Cuthbert filed the second Canadian challenge, bankrolling, designing and sailing the first sloop challenge for the America's Cup in 1881. The small Canadian challenger Atalanta (84 tons, 1881), representing the Bay of Quinte Yacht Club, suffered from lack of funds, unfinished build and a difficult delivery through the Erie Canal from Lake Ontario to New York. In contrast, the NYYC cautiously prepared its first selection trials. The iron sloop Mischief (79 tons, 1879 design by Archibald Cary Smith) was chosen from four sloop candidates and successfully defended the cup.

1885–1887: The NYYC Rule

In response to the unsuccessful Canadian challenges, the Deed of Gift was amended in 1881 to require that challenges be accepted only from yacht clubs on the sea. The Deed was further amended to provide that challenger yachts must sail to the venue on their own hull. Furthermore, Archibald Cary Smith and the NYYC committee devised a new rating rule that would govern the next races. They included sail area and waterline length into the handicap, with penalties on waterlines longer than . Irish yacht designer John Beavor-Webb launched the challengers Genesta (1884) and Galatea (1885), which would define the British "plank-on-edge" design of a heavy, deep and narrow-keel hull, making for very stiff yachts ideal for the British breeze. The boats came to New York in 1885 and 1886 respectively, but neither would best the sloops Puritan or Mayflower, whose success in selection trials against many other candidates proved Boston designer Edward Burgess was the master of the "compromise sloop" (lightweight, wide and shallow hull with centerboard). This design paradigm proved ideal for the light Yankee airs.

In 1887, Edward Burgess repeated his success with the Volunteer against Scottish yacht designer George Lennox Watson's challenger Thistle, which was built in secret. Even when the Thistle was drydocked in New York before the races, her hull was draped to protect the secret of her lines, which borrowed from American design. Both Volunteer and Thistle were completely unfurnished below decks to save weight.

1889–1903: The Seawanhaka Rule In 1887, the NYYC adopted the Seawanhaka Corinthian Yacht Club's rating rule, in which Bristol, RI, naval architect Nathanael Herreshoff found loopholes that he would use to make dramatic improvements in yacht design and to shape the America's Cup's largest and most extreme contenders. Both Herreshoff and Watson proceeded to merge Yankee sloop design and British cutter design to make very deep S-shape fin-keeled hulls. Using steel, tobin bronze, aluminium, and even nickel for novel construction, they significantly lengthened bow and stern overhangs, further extending the sailing waterline as their boats heeled over, thus increasing their hull speed.

The next America's Cup challenge was initially limited to waterline in 1889, but the mutual-agreement clauses of a new 1887 Deed of Gift caused the Royal Yacht Squadron to withdraw the Earl of Dunraven's promising Watson designed challenger Valkyrie while she was crossing the Atlantic. Dunraven challenged again in 1893, pleading for a return to the longer limit. In a cup-crazed Britain, its four largest cutters ever were being built, including Watson's Valkyrie II for Dunraven's challenge. Meanwhile, the NYYC's wealthiest members ordered two cup candidates from Herreshoff, and two more from Boston yacht designers. Charles Oliver Iselin, who was running the syndicate behind one of the Herreshoff designs called Vigilant, gave the naval architect leave to design the yacht entirely as he willed. Herreshoff helmed Vigilant himself and beat all his rivals in selection trials, and defended the cup successfully from Valkyrie II.

Urged to challenge again in yet larger boat sizes, Dunraven challenged again in 1895 with a waterline limit. The Watson designed challenger Valkyrie III received many innovations: She would be wider than the defender, and featured the first steel mast. The NYYC ordered another defender from Herreshoff, which he had built in a closed off hangar and launched at night so as to conceal her construction: Defender used an aluminium topside riveted to steel frames and manganese bronze below waters. This saved 17 tons of displacement, but later subjected the boat to extreme electrolysis after the Cup races. Valkyrie III lost the first race, was deemed disqualified in the second race following a collision with Defender before the start line despite finishing first, and in turn withdrew from the contest. The unraveling of the races left Dunraven in a bitter disagreement with all parties over fairness of the cup committee concerning claims. After he asserted that he had been cheated, his honorary membership of the NYYC was revoked. Henry "Hank" Coleman Haff, was inducted into America's Cup Hall of Fame in 2004 for his sailing of Defender in 1895 and bringing the cup back. At age 58, Hank Haff was the oldest cup winner in the history of the race.