The personal informatics field claims many potential benefits for users, from self-reflection to self-improvement. However, despite this focus on the self, the personal informatics literature has given little attention to how the self is conceptualised in tool design. From a starting point that all notions of the self are socially constructed, we draw on critiques of the PI literature to track three key conceptualisations of the self that are prevalent in the personal informatics literature – the unitary self, the lacking self, and the knowable self. For each of these, we suggest a possible design space opened by embracing an alternative conception of the self: design for fluidity and fragmentation; design for “human-ness”; and dialogical design. These design spaces offer some future directions for personal informatics that take seriously recent critiques of the field and, in centering how the self is conceptualised, provide alternative research approaches for personal informatics.