This article discusses the cameras – mainly 35 mm SLRs – manufactured by Pentax Ricoh Imaging Corp. and its predecessors, Pentax Corporation and Asahi Optical Co., Ltd. . Pentax must not be confused with Pentax 6x7 or Pentax 67 which are 120 medium format 6x7cm film cameras.

The M42 lens mount is a screw thread mounting standard for attaching lenses to 35 mm cameras, primarily single-lens reflex models. It is more accurately known as the M42 × 1 mm standard, which means that it is a metric screw thread of 42 mm diameter and 1 mm thread pitch.