This project traces how the Mexican Catholic Church opened itself to tolerating and embracing indigenous catholicisms, how activists built a Catholic multiculturalism from the ground up (1960s-1990s), and how the Vatican recognized their decades of work by accepting Náhuatl as an official liturgical language in 2015. This history is inseparable from the Latin American experiences of Liberation Theology, its theological offshoot of Indigenous Theology, and the progressive Catholics who insisted that the Catholic Church could shed a reputation of serving the rich to instead opt for the poor, the marginalized, and the indigenous. A pair of questions guided this project. What impact did Liberation Theology and its practitioners have on rural, indigenous Mexico? How did the concrete actions and experiences of indigenous peoples shape the pastoral programs and cultural-political orientation of Mexico’s Catholic Church? Beginning in the mid-century, Church hierarchs vied over approaches to the “indigenous question.” Following the reforms of the Second Vatican Council, the Bishops of the Pacific South Region opened a regional seminary, SERESURE (1969-1990), in Tehuacán, Puebla to train priests to work in the indigenous realities of the region. I argue that the everyday interactions between progressive Catholics from SERESURE and indigenous Nahua villages created a multicultural pastoralism that tried to alleviate the economic crisis of neoliberal structural change and incorporated indigenous culture and religiosity into Mexican Catholicism. My dissertation challenges a historiographical focus on the conservative elements of Mexican Catholicism to reveal ideological struggle within the institution and show how progressives shaped the Church. I redirect the geographical focus of analysis on Mexican Liberation Theology away from Bishop Samuel Ruiz in Chiapas and toward a regional project of progressive Catholics centered in Tehuacán, Puebla. I innovate on studies of religion and social reform in late twentieth century Mexico by foregrounding how indigenous popular religiosity shaped liberationist activism. I also reassess the long term reverberations of Liberation Theology in Latin America and argue that the indigenous cultural activism of progressive Catholics in southern Mexico shaped the multiculturalism that emerged in the transition to neoliberalism at the end of the Cold War.