Abstract: An interchangeable ring system jewelry (20) consisting of a custom ring assembly (18) which can be assembled according to the user's desire, manually or by using specific tools (28L, 28R). The custom ring assembly (18) is comprised of an elongated flanged ring shank (22), an inner threaded nut-like interlocking ring (26), and an interchangeable inner ring (24). The flanged ring (22) in its preferred configuration is comprised of a fixed flange ring (36), fixed to one of its ends, and an external thread (32) on the other end. The inner ring (24) is slid onto the flanged ring shank (22), up to the fixed flange ring (36). The interlocking ring (26) interlocks to the flanged ring shank (22), screwed to its threaded end using specific tools (28L, 28R) or manually. In this way, the inner ring (24) is delimited between the interlocking ring (26) and the fixed flange ring (36) of the flanged ring shank, creating ready-to-wear custom ring jewelry.