John III Ducas Vatatzes (1193 - November 3, 1254) was Byzantine Emperor, in exile in the Empire of Nicaea, from 1222 to 1254.

He earned for himself such distinction as a soldier that in 1222 he was chosen to succeed his father-in-law Theodore I Lascaris.

He reorganized the remnant of the Byzantine Empire, and by his administrative skill made it the strongest and richest principality in the Levant. Having secured his eastern frontier by an agreement with the Seljuk Turks, he set himself to recover the European possessions of his predecessors. While his fleet harassed the Latins in the Aegean Sea and extended his realm to Rhodes, his army, reinforced by Frankish mercenaries, defeated the Latin emperor's forces in the open field.

Though unsuccessful in a siege of Constantinople, which he undertook in concert with the Bulgarians (1235), he obtained supremacy over the despotates of Thessalonica and Epirus. The ultimate recovery of Constantinople by the Byzantine emperors is chiefly due to his exertions.

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Preceded by Theodore I Lascaris

Byzantine Emperor in exile in the Empire of Nicaea

Succeeded by Theodore II Lascaris

This article incorporates text from the public domain 1911 Encyclop�dia Britannica.

de:Johannes III. (Byzanz) ja:ヨハネス3世ドゥーカス・ヴァタツェス pl:Jan III Watatzes