Syrmia County (Croatian: Srijemska županija, Serbian: Сремска жупанија, Hungarian: Szerém vármegye, German: Komitat Syrmien) was a historic administrative subdivision (županija) of the Kingdom of Croatia-Slavonia.

Croatia-Slavonia was an autonomous kingdom within the Lands of the Crown of Saint Stephen (Transleithania), the Hungarian part of Austria-Hungary.

The entire region was incorporated into the Military Frontier, which was then extended from Western Slavonia, where it stood in 1683, all the way to Transylvania.

[2] After 1860, Syrmia County was established again, and was reincorporated into the Kingdom of Slavonia, which was a completely separate Habsburg province at the time.

After World War I, the area of Syrmia County became part of the newly formed Kingdom of Serbs, Croats and Slovenes in 1918 and this was confirmed by the Treaty of Saint-Germain in September 1919.