The invention relates to an endoscope comprising: a shaft (2) that is designed as a flexible or rigid elongate hollow body； a main part (3) in which said shaft (2) is received by its proximal end (5)； an optical waveguide (7) and a working channel (10) which extend through the shaft (2) from the distal end to the proximal end, continuing in the main part (3), said working channel (10) receiving an instrument； a distal end (11) of the working channel (10) which is in the region of the distal end (6) of the shaft (2)； and a proximal end (12) of the working channel (10) which is in or on the main part (3), wherein the cross-section of the working channel (10) is circular at its proximal end (12) and non-circular at its distal end (11), and the working channel (10) comprises a transition region (18) in which the circular cross-section transitions into the non-circular cross-section.
