The Peruvian altiplano, a high plateau around Lake Titicaca, is known for its breathtaking landscapes and the cultivation of commodities like quinoa and alpaca wool. The region also stands out for its history of inter-Indigenous language contact and multilingualism between Quechua- and Aymara-speaking communities. This linguistic ecology predates the Spanish conquest and persists today, making the altiplano, with its capital, Puno, a unique space where Indigenous multiplicity is recognized and celebrated. Yet this celebration is accompanied by additional ideological challenges around defining Quechua and Aymara as distinct Indigenous languages and ethnic groups. Anthropologist Sandhya Krittika Narayanan begins with these challenges, and asks: What does it mean to be a Quechua or Aymara speaker in Puno today? What does it mean to be an Indigenous ethnic Quechua or Aymara individual? Mother Tongues of the High Andes opens with these questions, exploring what Quechua and Aymara languages and identities mean for Indigenous puneños as they navigate their past and present. Narayanan argues that understanding inter-Indigenous linguistic and social differences involves examining Indigenous gender roles, responsibilities, and linguistic practices, particularly those of Indigenous puneña women. She shows how these practices have contributed to the maintenance of Indigenous multilingualism and continuity in local modes of understanding Indigenous identity and difference. Even as ideologies around Indigenous identity and linguistic practices shift due to global discourses on Indigenous ethnic identity and nationalism, Indigenous women continue to play a crucial role, promoting new ways to speak and think about Quechua and Aymara linguistic differences, making the Indigenous roots and histories of Puno recognizable to a global audience. Through a comprehensive ethnographic exploration of gender, language, and Indigenous difference, Narayanan shows how the linguistic and social practices of Indigenous puneña women both contest and reaffirm competing visions of Quechua and Aymara linguistic identity and authority.