Swiss politician
Johann Theodor Kaspar Rudolph Ambros Alois Xaver Ab Yberg or more compactly Theodor Ab Yberg (8 December 1795, Schwyz - 30 November 1869) was a Swiss statesman.
Theodor is the son of alderman Alois Xaver Ab Yberg and his wife Maria Anna von Reding. He served in the Swiss Guard in Paris, but returned home in 1823. After having been member of the cantonal court, he was elected alderman in 1826. In 1830 he became governour of the Schwyz district and as well the canton. 
In a dispute between the outer districts of Schwyz who demanded equal rights under the Constitution and the "old lands", he fervently vindicated the supremacy of the latter. Thereby he gained the esteem of his fellow countrymen. When the council decided to occupy Küssnacht in the then existing district "Schwyz outer lands" in August 1833, Ab Yberg was the leading commander of the troops. The assault failed though, as did a simultaneous from Basel, and he forfeited his military rank of colonel.
As a result of the attack on Küssnacht, the canton Schwyz was occupied by the confederate Swiss army. On 11 October 1833 it was reunited with the outer Schwyz under equal rights in the constitution. On 3 November, Ab Yberg was reelected head of the district council, in 1834, 1838, 1842 and 1846 head of the canton ("Landammann").
On 26 September 1847 he was elected main commandant of the Schwyz troops. With the fall of the "Sonderbund", a special alliance between seven Swiss cantons, he disappeared from the political scene. In 1852 he was once more elected into the cantonal council, but could not keep up with the political changes and retired soon thereafter and went to exile in Austria. 