A spark plug comprising: an insulator having formed therein an axial hole extending from front to rear in a direction along an axial line, the insulator including a stop portion overhanging radially outward; a metal shell disposed around the insulator and including a stepped portion protruding radially inward, the stepped portion stopping the stop portion from a front side thereof directly or with another member therebetween; and a center electrode disposed in the axial hole, the center electrode including a front end portion located forward of a front end of the insulator and a tip welded to the front end portion with a fused portion therebetween, wherein the front end portion contains Ni, Cr, and at least one element selected from a group B consisting of Mn, Si, Al, Ti, rare earth elements, Hf, and Zr, Ni being present in the largest proportion, Cr being present in the second largest proportion and in an amount of 12% by mass or more, the at least one element selected from the group B being present in a total amount of 0.1% by mass or more, the front end portion satisfying f/e ≤ 0.15 and m/e ≤ 0.015, where f is an Fe content, e is a sum of Cr, Si, and Al contents, and m is a Mo content, and characterised in that the spark plug has a distance D of 22 mm or less in the direction along the axial line from a first point located at a frontmost position of a boundary between an outer surface of the front end portion and an outer surface of the fused portion to a second point located at a frontmost position of a contact area between the stepped portion or the other member and the stop portion. an insulator having formed therein an axial hole extending from front to rear in a direction along an axial line, the insulator including a stop portion overhanging radially outward; a metal shell disposed around the insulator and including a stepped portion protruding radially inward, the stepped portion stopping the stop portion from a front side thereof directly or with another member therebetween; and a center electrode disposed in the axial hole, the center electrode including a front end portion located forward of a front end of the insulator and a tip welded to the front end portion with a fused portion therebetween, wherein the front end portion contains Ni, Cr, and at least one element selected from a group B consisting of Mn, Si, Al, Ti, rare earth elements, Hf, and Zr, Ni being present in the largest proportion, Cr being present in the second largest proportion and in an amount of 12% by mass or more, the at least one element selected from the group B being present in a total amount of 0.1% by mass or more, the front end portion satisfying f/e ≤ 0.15 and m/e ≤ 0.015, where f is an Fe content, e is a sum of Cr, Si, and Al contents, and m is a Mo content, and characterised in that the spark plug has a distance D of 22 mm or less in the direction along the axial line from a first point located at a frontmost position of a boundary between an outer surface of the front end portion and an outer surface of the fused portion to a second point located at a frontmost position of a contact area between the stepped portion or the other member and the stop portion.