Ruins is a Japanese minimalist prog duo of drum set and electric bass guitar. The group, formed in 1985, was supposedly intended to be a power trio; the guitarist, however, never showed up to the band's first rehearsal, so the group remained a duo. The drummer is Tatsuya Yoshida and the group has featured four different bass players over its history.

The French progressive rock band Magma is the group's most important influence, to such an extent that Ruins' original lyrics are written and sung in an invented language which, at first glance, resembles Kobaïan, the language invented by Christian Vander of Magma. Ruins' material (which Yoshida, who composes the majority of their pieces, writes out in score form) is generally of extreme complexity and thus is often described as inaccessible - potential listeners may be bewildered by the band's unrestrained yet disciplined approach, or simply astounded by the visceral energy of the pair.