Abstract: Recent research attests to the importance of three distinct orientations to happiness-pleasure, engagement, and meaning - which together integrate hedonic and eudaimonic approaches to the good life (Peterson et al. 2005; Ryan & Deci, 2001; Seligman 2002). This chapter considers the concept of meaning in life, a crucial variable for physical health and psychological adjustment in a variety of contexts. The growing focus on positive psychology in recent years has signified a renewed interest in the health benefits of personal meaning, or purpose in life, yet fundamental questions about these concepts remain. Whilst clinical, existential, and humanistic perspectives on the absence or acquisition of meaning in life have all helped lay foundations for attempts at a formal definition, they often disagree over potential criteria for inclusion in the meaning in life construct. Different philosophical and psychological traditions have variously equated meaning in life with certain positive affects, purpose in life, success, personal growth, self-actualisation and a sense of coherence. Furthermore, theories of positive psychological health, motivation, lifespan development, and maturity have all come to incorporate an understanding of meaning in life, resulting in a vast array of conceptualised and operationalised terms. This chapter therefore addresses the need to delineate the phenomenology, antecedents, and consequences of meaning in life from multiple converging and diverging perspectives. It evaluates possible criteria for inclusion in the meaning in life concept, in terms of their philosophical underpinnings and psychological research applications. I examine the extent that these multiple perspectives converge by considering popular psychometric measures of existential meaning and highlighting various measurement issues in the field of meaning research. I then describe the development of the Meaningful Life Measure (Morgan & Farsides, 2009), with its five components of personal meaning - valued life, principled life, purposeful life, accomplished life and exciting life - and discuss its practical and theoretical implications for future research.