Excalibur is a French progressive rock band known for its unique incorporation of Celtic folk elements. Founded by Alan Simon in 1998, the band is renowned for its "Excalibur" quadrilogy, a series of concept albums based on Arthurian legends that have showcased a rotating cast of prominent musicians. The band's signature sound is characterized by intricate instrumental arrangements, harmonized vocals, and thematic storytelling, making them a significant contribution to the progressive rock genre. Excalibur's innovative fusion of progressive rock and Celtic folk has influenced numerous bands in the European music scene.