The (Greek, Ancient (to 1453);: τατᾶς), more formally the (Greek, Ancient (to 1453);: τατᾶς τῆς αὐλῆς||{{transl|grc|tatas) was a Byzantine court office attested in the 12th–14th centuries, whose exact functions are unclear.
The title is first attested in the seal of John Komnenos Vatatzes in the 12th century, and over the next two centuries. Nevertheless, the exact functions it entailed are unclear: according to the 14th-century historian Pachymeres, the was one of the three major court functionaries along with the (imperial cup-bearer) and the (master of the imperial table), but the 15th-century historian Doukas explains the title as "pedagogue". This led Ernst Stein to suggest that he succeeded the as imperial preceptor, a hypothesis rejected later by Vitalien Laurent.