The Pentax K1000 is an interchangeable lens, 35 mm film, single-lens reflex (SLR) camera, manufactured by Asahi Optical Co., Ltd. from 1976 to 1997, originally in Japan. The K1000's extraordinary longevity makes it a historically significant camera. The K1000's inexpensive simplicity was a great virtue and earned it an unrivalled popularity as a basic but sturdy workhorse. The Pentax K1000 eventually sold over three million units.

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.