Colonialism’ and ‘decolonization’ have been dealt with by postcolonial studies and, more recently, by scholars identified with the ‘de-colonial turn’. At the same time, in the ethnopolitically charged context of contemporary Bolivian society, colonialism and decolonization have become issues of political, existential and even cosmological import. This thesis identifies a need to root the ‘de-colonial turn’ in specific lifeworlds and explores the dimensions of meaning that inform and lend existential and cosmological import to indigenous notions of colonialism and decolonization. The particular subjects with which this thesis engages may be pinned down to four points: Firstly, the thesis is a close-up study of the notions of colonialism and decolonization held by ethnopolitically engaged ritual specialists and their young apprentices in contemporary Aymara society. It also examines the cosmological framework within which such notions are formed, understood and awarded meaning. Secondly, it is a study of ‘decolonizing practices’ and of the relation between ‘ritual practice’ and ‘cosmological knowledge’ as well as of the existential implications of ritual and its transformative experiences for the young apprentices. Thirdly, this thesis compares the notions of colonialism, decolonization and the decolonizing practices of the ritual specialists and apprentices with official state discourse on colonialism and decolonization and the ‘decolonizing politics’ launched by the Evo Morales administration. Fourthly, the thesis explores how Aymara cosmological notions of ‘illness’ and ‘cure’, ‘self’ and ‘other’ are located within fields of national political power, ethnopolitical ideologies and indigenous mobilizations. It inquires into how ethnopolitical notions of the world are informed by such cosmological notions while simultaneously being incorporated into the cosmological world of the Aymara ritual specialists.