The Yaghnob Valley is a valley in north-west Tajikistan, between the southern slope of the Zarafshan Range and the northern slope of the Gissar Range.
The valley is formed by the Yaghnob River and belongs to the Zarafshan basin. It lies between 2,500 and 3,000 metres above sea level and is virtually inaccessible for six months of the year.
Yaghnobi is an Eastern Iranian language spoken in the upper valley of the Yaghnob River in the Zarafshan area of Tajikistan by the Yaghnobi people. It is considered to be a direct descendant of Sogdian and has sometimes been called Neo-Sogdian in academic literature. There are some 12,500 Yaghnobi speakers, divided into several communities. The principal group lives in the Zafarobod area. There are also resettlers in the Yaghnob Valley. Some communities live in the villages of Zumand and Kůkteppa and in Dushanbe or its vicinity.
Most Yaghnobi speakers are bilingual in Tajik, a dialect of Persian. Yaghnobi is mostly used for daily family communication, and Tajik is used by Yaghnobi-speakers for business and formal transactions. A Russian ethnographer was told by nearby Tajiks, long hostile to the Yaghnobis, who were late to adopt Islam, that the Yaghnobis used their language as a "secret" mode of communication to confuse the Tajiks. The account led to the assumption by some that Yaghnobi or some derivative of it was used as a secret code.