This entry addresses the Mongolic elements in the Siberian Turkic varieties. This is an important aspect of Altaic studies, since the problem of genealogical relations between languages of an Altaic language family is still regarded as unresolved. Addressing this will only be possible if we first examine the loanwords and separate loans from items of possible common origin. The entry consists of two parts, dealing with (i) the phonetic criteria of Mongolic elements in Siberian Turkic and (ii) Mongolic elements of Turkic origin or re-borrowings from Turkic. The aim of the first part is to present how the main phonetic features of Middle Mongol sources and modern Mongolic languages can help to determine the approximate period of borrowing. There are two evident layers of copying: the early one includes Turkic loanwords with Mongolic features particular to Middle Mongol sources (13th c.–16th c.), while the later layer includes loanwords with typical modern Mongolic, Khalkha, Buryat, or Oyrat features. The early layer also comprises elements in Siberian Turkic, which underwent phonetical sound changes valid in the copying Turkic language. The second part of the paper focuses on the various phonetic, morphological, and semantic criteria to determine a special group of Mongolic loanwords in Siberian Turkic that comprises elements of ultimately Turkic origin.