One Hour is the eleventh full-length album by German electronic music outfit Cluster. It was recorded live in the studio in Vienna, Austria in July, 1994 and released on January 24, 1995 on the U.S. based Gyroscope label. Precisely one hour of music was culled from four hours of improvisation in the studio. The music is continuous and One Hour is presented as a single piece, the longest Cluster has recorded to date.