A steering system comprising: a steering shaft configured to extend and contract in a column axial direction; a column jacket that includes a lower jacket and an upper jacket fitted in the lower jacket and that is configured to extend and contract in the column axial direction; a first tooth defining member that has first teeth arranged in the column axial direction and that moves together with the upper jacket; and a second tooth defining member including a first portion rotatably supported around a support so as to be movable in the column axial direction and such that movement of the first portion in an orthogonal direction orthogonal to the column axial direction is regulated and a second portion located away from the first portion in the column axial direction and having second teeth coming into meshing engagement with the first teeth to achieve telescopic locking; characterized by a guide mechanism that guides the second portion in an inclination direction inclined with respect to the orthogonal direction, wherein the guide mechanism includes a guide shaft supported by the lower jacket, and a guide hole that is slot formed in the second portion and extending in the inclination direction such that the guide shaft is inserted through the slot, the guide hole having a first end and a second end arranged farther from the second teeth than the first end and above the first end in the column axial direction, and the guide shaft is sheared, at a time of a secondary collision, by a load imposed via the first and second teeth that are in a meshing engagement state, permitting the first tooth defining member and the second tooth defining member to move together. a steering shaft configured to extend and contract in a column axial direction; a column jacket that includes a lower jacket and an upper jacket fitted in the lower jacket and that is configured to extend and contract in the column axial direction; a first tooth defining member that has first teeth arranged in the column axial direction and that moves together with the upper jacket; and a second tooth defining member including a first portion rotatably supported around a support so as to be movable in the column axial direction and such that movement of the first portion in an orthogonal direction orthogonal to the column axial direction is regulated and a second portion located away from the first portion in the column axial direction and having second teeth coming into meshing engagement with the first teeth to achieve telescopic locking; characterized by a guide mechanism that guides the second portion in an inclination direction inclined with respect to the orthogonal direction, wherein the guide mechanism includes a guide shaft supported by the lower jacket, and a guide hole that is slot formed in the second portion and extending in the inclination direction such that the guide shaft is inserted through the slot, the guide hole having a first end and a second end arranged farther from the second teeth than the first end and above the first end in the column axial direction, and the guide shaft is sheared, at a time of a secondary collision, by a load imposed via the first and second teeth that are in a meshing engagement state, permitting the first tooth defining member and the second tooth defining member to move together.