SIAT may refer to:

• S.I.A.T. (Sociedad Ibérica de Automóviles de Turismo), the predecessor company of the Spanish car maker SEAT (S.E.A.T., Sociedad Española de Automóviles de Turismo)
• Siebelwerke/ATG, a German aircraft manufacturer
• Sibaviatrans, a Russian airline
• N-acetyllactosaminide alpha-2,3-sialyltransferase, an enzyme

Siat is a former municipality in the district of Surselva in the Swiss canton of Graubünden. On 1 January 2014 the former municipalities of Siat, Castrisch, Ilanz, Ladir, Luven, Pitasch, Riein, Ruschein, Schnaus, Sevgein, Duvin, Pigniu and Rueun merged into the new municipality of Ilanz/Glion.

SIAT may refer to:

• S.I.A.T. (Sociedad Ibérica de Automóviles de Turismo), the predecessor company of the Spanish car maker SEAT (S.E.A.T., Sociedad Española de Automóviles de Turismo)
• Siebelwerke/ATG, a German aircraft manufacturer
• Sibaviatrans, a Russian airline
• N-acetyllactosaminide alpha-2,3-sialyltransferase, an enzyme

Siat is a former municipality in the district of Surselva in the Swiss canton of Graubünden. On 1 January 2014 the former municipalities of Siat, Castrisch, Ilanz, Ladir, Luven, Pitasch, Riein, Ruschein, Schnaus, Sevgein, Duvin, Pigniu and Rueun merged into the new municipality of Ilanz/Glion.