Tangam is a critically endangered Trans-Himalayan (Tibeto-Burman) language spoken by around 150 hilltribespeople in the far Eastern Himalaya. A member of the Tani subgroup of Trans-Himalayan, Tangam is mutually-unintelligible with other languages of this otherwise relatively homogeneous subgroup. This is demonstrated to be a consequence of Tangam's early-branching status within the Western Tani subgroup, subsequent contact with Eastern Tani languages, and historical relationship with speakers of Bodic languages. Based on three field trips to the Tangam-speaking area over two years, this work presents a brief but comprehensive cultural, historical and grammatical introduction to the Tangam language, together with a trilingual lexicon in Tangam, English and Minyong, and a collection of fully-analysed texts. It will be of interest to linguists and anthropologists of the Himalayan region, as well as to historical linguists and language typologists.