Ioannes III ( el, , ''Iōannēs G΄'') may refer to:
*
Patriarch John III of Constantinople (died in 577)
*
John III Doukas Vatatzes
John III Doukas Vatatzes, Latinized as Ducas Vatatzes ( el, Ιωάννης Δούκας Βατάτζης, ''Iōannēs Doukas Vatatzēs'', c. 1192 – 3 November 1254), was Emperor of Nicaea from 1221 to 1254. He was succeeded by his son, known ...
(c. 1192–1254), Byzantine Emperor
*
John III Megas Komnenos (c. 1321–1362), Emperor of Trebizond
See also
*
John III (disambiguation) John III may refer to:
People
* John III (bishop of Jerusalem) in 516–524
* Pope John III, Pope from 561 to his death in 574
* John Scholasticus, Patriarch of Constantinople from 565 to his death in 577
* John III Rizocopo, Exarch of Ravenna fr ...
{{DEFAULTSORT:Ioannes 03