An endoscope system (100) includes an endoscope (10), and an insertion auxiliary tool (50) into which the endoscope is inserted. A flexible portion (36) of the insertion section (12) of the endoscope includes, from a distal end side toward a proximal end side, a low flexural rigidity portion (36A), a flexural rigidity varying portion (36B) in which a flexural rigidity increases from the distal end side toward the proximal end side, and a high flexural rigidity portion (36C) with flexural rigidity higher than that in the low flexural rigidity portion (36A). When at least a part of the flexible portion (36) projects from a distal end opening (56) of the tube body (54), a proximal end position of the low flexural rigidity portion (36A) is on a proximal end side of the tube body (54) with respect to the distal end opening (56).
