We develop a theory of authentic self-leadership (ASL) that connects authentic leadership with self-leadership and identifies its relationship to meaningful and engaging work and to wellbeing. We identify two dimensions of authentic self-leadership, i.e., authentic self-awareness and authentic self-expression, that managers can apply to their own self-awareness, behaviors, and relations with others. These dimensions describe self-leadership in terms of “know thyself” authenticity and “be thyself” authenticity. Empirical testing of the theoretical model showed support for eight out of the eleven hypotheses derived from the theory. Authentic self-awareness did not have a significant effect on either meaningful work or employee engagement, nor did meaningful work have a significant effect on subjective happiness. All other hypotheses were supported by the data. Authentic self-leadership (ASL) theory addresses some of AL theory’s key limitations and helps us understand how to increase meaningful and engaging work, as well as managerial wellbeing.