Idrottsföreningen Elfsborg, also known as IF Elfsborg or simply Elfsborg, is a professional football club based in Borås, Sweden, and is affiliated to the Västergötlands Fotbollförbund. They play in the Allsvenskan and have spent most of their history in the top tier of Swedish football. Their homeground is Borås Arena, where they have played since 17 April 2005.
The club was founded in 1904 by a group of 19 youngsters which all were 14–15 years old. Borås Fotbollslag was formed in Ordenshuset at Landala on 26 June 1904. The main protagonist in the formation, Carl Larson, who in addition to football also practiced athletics and wrestling. Claimed the reason was that the main sports club in the city, Borås Athletic and Sports Society, would not exert football in their program.
Carl Larson, however, found that there were too many clubs containing the city name Borås which contributed to the name change in 1906 by Riksidrottsförbundet to the current, IF Elfsborg. The name is derived from Älvsborg County where instead of making use of the modern spelling Älvsborg, they used out of the older spelling with an E.