Western health professions have historically struggled with the notion that spirituality could be studied empirically. This trend has changed in recent decades with there being a marked increase in the health literature pertaining to spirituality. For indigenous people spirituality is a fundamental attribute of their worldviews. Mäori, as the Indigenous people of Aotearoa, have always acknowledged the importance of wairua, (spirituality as defined by Mäori worldviews) to their health and well-being. This thesis aims to explore wairua as an important aspect of Mäori well-being from a psychological perspective. Two research goals underpin this thesis. The first goal involved developing an understanding of what Mäori mean when they talk about wairua. This was achieved through a qualitative study. While there are implicit shared understandings among Mäori regarding the nature of wairua, this study was one of the first attempts to make some of those shared understandings more explicit. The second goal involved investigating the relationship between an orientation to wairua and Mäori well-being using a newly developed measure. This was a quantitative study. Conceptualisations of wairua fell into four themes; direct descriptions, personal experiences, personal beliefs and Mäori worldviews. According to the qualitative information, wairua was described as a fundamental attribute that enables Mäori to engage with their reality; an intuitive consciousness. Through wairua Mäori identity is expressed, relationships are forged, balance is maintained, restrictions and safety are adhered to, healing is transmitted, and the connection between te ao wairua and te ao Mäori are maintained. These aspects of Mäori reality are inclusive and interconnected. The qualitative study information led to the formation of a 30 item self report measure named the Kia Ngawari ki te Awatea Orientation to Wairua measure. This measure was used to investigate the relationship between an orientation to wairua and Mäori health and well-being. The results showed that orientations to wairua had relatively modest associations with wellbeing when conceptualised and measured in a variety of ways. Due to the variability in the results, support for the overarching hypothesis of a relationship between wairua and well-being was mixed. A number of limitations were acknowledged with recommendations for future research offered. The findings of these studies have a number of implications for clinical psychological practice with Mäori clients.