A sideways viewing endoscope including: a proximal handle, an endoscope shaft having outer and inner tubes, and first and second optical component assemblies arranged in a distal region of the endoscope shaft, the optical components assemblies can be rotated with respect to one another about a longitudinal axis of the endoscope shaft and are mounted against each other by an axial bearing that is disposed between the optical component assemblies and pretensioned by a pretensioning device wherein the first optical component assembly is distally connected to the outer tube and comprises optical windows, prisms and/or lenses having a sideways viewing direction and the second optical component assembly is distally connected to the inner tube and comprises an image sensor having a straight-ahead viewing direction oriented in the direction of the longitudinal axis and the pretensioning device is disposed in the distal region of the endoscope shaft at the axial bearing.
