Kalto or Nahali is a poorly documented language of west-central India. Kuiper (1962) conjectured that it is unrelated to any other Indian language but, even if that is so, its vocabulary has over the millennia been heavily influenced, in turn by Munda, Dravidian and latterly, Indo-European Marathi. In Victorian times the Kalto (then known disparagingly as "Nahals" or "Nihals") were among the most notorious of the wild jungle tribes that lived by plunder. Just after 1800 an Arab princeling of the Moghul empire led a punitive expedition against them that destroyed their tribal independence. Their tribal area is just south of the Tapti river, around the village of Tembi in Nimar district of Chota Nagpur, Madhya Pradesh.

Kalto is possibly related to another near-extinct remnant of the Indian linguistic sub-stratum, namely Kusunda, spoken in southwest Nepal. Michael Witzel of Harvard asserts, quoting Shafer and Kuiper, a relationship to Ainu