William Alcock (30 June 1861 – 31 August 1915) was a Scottish footballer who was the first captain of Spanish club Recreativo de Huelva, leading his side in the first official football match in Spain in 1890,^[1] and later led the club to its first-ever piece of silverware in 1904.^[2]

Despite not being one of the founding members of Recreativo de Huelva in December 1889, he was nonetheless the team's captain when the club faced Sevilla FC just three months later, on 8 March 1890, at the Hipódromo de Tablada (horse racing track), which ended in a 2–0 loss.^[1][3][4][5] This match is now considered to be the first official football match in Spain, which means that Alcock was the first official captain in Spanish football history alongside Sevilla's Hugh MacColl.^[1][3] In most of the sources listing the line-ups of this match, Alcock and MacColl are the first to appear, leading many to assume that they were the goalkeepers, which is untrue.^[3] Even though Huelva lost, it is fair to point out that Alcock's team had never played together before, and that they had just returned from a four-hour train journey the same morning as the match, and that the match was refereed by Edward F. Johnston, the president of Sevilla FC.^[3]

On 20 February 1892, he lined up for Huelva as a forward in a friendly match against Sevilla FC, which had been set to serve as a tie-breaker between the two teams, since their previous two encounters had ended in a draw; Huelva won 2–0.^[6] Three months later, on 6 May, he again started as a forward for Huelva, this time in a match against Rio Tinto FC, playing alongside the likes of George Wakelin, Luis Birchall, and James Reeves.^[7][8] In the press of Huelva, he was sometimes referred to as Guillermo Alcock.^[6]

On 20 November 1904, Alcock captained Huelva to a victory over the British sailors of the Seamen's Institute, thus winning the so-called Copa Seamen's Institute, a silver cup that had been donated by Recreativo's vice-president José Muñoz Pérez, similar to how King Alfonso XIII had donated a trophy to the winners of the Copa del Rey, which had been founded only a year earlier.^[2] Despite some indications that the club had lifted the Copa de la Raza in 1893 and the Copa Heráldica in 1898, it can be reliably and based on strict documentary evidence that the Copa Seamen's Institute was the first time that a captain of Recreativo lifted a trophy, with Alcock doing that near the Anglican Chapel of the "Seamen's Institute".^[2] This trophy is the oldest that Recreativo has in its museum.^[2]

In the general guide of "Huelva and its Province" of 1917, don Guillermo J. Alcock is listed as a consular agent residing in Carretera Odiel, 43, in Huelva.^[9] Alcock also had a chalet near Hotel Colón.^[10]

In December 2014, the American sports media ESPN compared Huelva's first-ever line-up, including Alcock, to the starting line-up of the Spanish football team in the final of the 2010 FIFA World Cup.^[11]