Theodor Körner, Edler von Siegringen (German pronunciation: [ˈteːoˌdoːɐ̯ ˈkœʁnɐ] ⓘ; 23 April 1873 – 4 January 1957) was an Austrian military officer and statesman of the Social Democratic Party of Austria.

He served as an officer in Agram (today Zagreb, Croatia) and was promoted to major in 1904, in which year he became a member of the Austrian staff.

[5] Körner was a member of the Technischer Ausschuss (Technical Committee) of the Republikanischer Schutzbund and, alongside Alexander Eifler, considered one of its two leading military strategists.

As opposed to Eifler, who favored a more streamlined and classic military organization for the Social-Democratic paramilitary, Körner proposed a strategic outline utilizing guerilla warfare and mass action in the case of a civil war.

A motor vessel, the MS Theodor Körner was built in 1965 and currently operates on the Danube River as a "Bike & Boat" cruise ship, accommodating 135 passengers plus crew.