Nafusi (also spelt Nefusi; or Tanfust) is a Berber language spoken in the Nafusa Mountains (), a large area in northwestern Libya. Its primary speakers are the Ibadi Muslim communities around Jadu, Nalut () and Yafran.
The dialect of Yefren in the east differs somewhat from that of Nalut and Jadu in the west. Old Nafusi phrases appear in Ibadite manuscripts as early as the 12th century.
The dialect of Jadu is described in some detail in Beguinot (1931). Motylinski (1898) describes the dialect of Jadu and Nalut as spoken by a student from Yefren.
It appears especially closely related to Sokni and Siwi to its east.