A flange bolt cutter for separating two connected flanges. The flange bolt cutter contains a circular saw blade pivotally connected to an adjustable flange band. The flange band contains an alignment ring for aligning the circular saw blade about the midpoint between two connected flanges. The flange bolt cutter is hydraulically operated. The adjustable flange band may be formed in two band sections hinged together and containing a rotatable bolt and handle for tightening and loosening the band sections around the flange connection.