This thesis examines the emergence of the left in Latin America at the turn of the century. In particular, it examines Latin America’s ‘left turn’ in light of the mobilisation of indigenous social movements in the region during the late 1980s and early 1990s. It is argued that indigenous movements entered into a political alliance with leftist parties in the lead up to the left turn in their respective countries. This alliance was predicated on the agreement that indigenous movements would mobilise support for the left within their social bases in return for prospective compensation from the left. This compensation came in the form of a promise by the parties to implement policies addressing indigenous demands if elected. It is argued that indigenous movements were ideologically compatible with the left based on other policies too, such as the redistribution of wealth and alleviation of inequality. Ultimately, the thesis finds that indigenous movements provided a valuable base of support for the left in Bolivia and Peru in particular. This can help to explain the electoral success of the left in some cases, thereby contributing to the scholarship on Latin America’ Left Turn. It is also suggested indigenous movements are more likely to support the extreme or ‘contestatory’ variants of the left rather than moderate forms which are less likely to implement radical redistributive policies and constitutional reform. In this way, the research contributes to the secondary puzzle that has emerged within the literature on Latin America’s left turn concerning the variation in the types of left which have emerged. Although the support by movements does not exclusively explain the emergence of the parties studied here, it was nonetheless an important contribution to their success. It is in this way that the thesis provides a missing piece of the puzzle of Latin America’s left turn. I term this missing piece ‘el factor indígena’, or the indigenous factor.