The 2007–08 Celtic League (known as the 2007–08 Magners League for sponsorship reasons) was the seventh Celtic League season and the second with Magners as title sponsor. The season began on 31 August 2007 and finished on the weekend beginning 10 May 2008. Some disruption to fixtures occurred as a result of the 2007 Rugby World Cup, which took place during September and October 2007.

The teams competing were the same as the previous season with one exception; only two Scottish teams participated, as the Scottish Rugby Union scrapped the Border Reivers region at the end of the 2006–07 season. As in previous seasons, the league was played on a home and away basis, with teams earning four points for a win, and a bonus point for scoring four or more tries in a match. The losing team may also earn a bonus point if they lose by seven points or less. The losing bonus point system is intended to ensure that both teams compete fully in all matches.

The ten teams competing were the four Irish provinces: Munster, Leinster, Connacht and Ulster; two Scottish regions: Edinburgh Rugby and Glasgow Warriors; and four Welsh regions: Llanelli Scarlets, Cardiff Blues, Ospreys and Newport Gwent Dragons.