A modular illumination device having an electronics assembly, an inner body portion extending from a first end to a second end and defining an interior cavity, wherein the inner body portion is formed so as to accept the electronics assembly within the cavity; a head assembly removably attached or coupled to the first end of the inner body portion; a tail cap portion removably attached or coupled to the second end of the inner body portion, wherein the tail cap portion includes a button assembly having a depressible button; and at least one body sleeve extending from a first end to a second end and defining an interior cavity, wherein the body sleeve is formed so as to accept the inner body portion within the cavity of the body sleeve and to be assembled between the head assembly and the tail cap portion.