Joannes Iv. La'scaris
（Ἰωάννης ὁ Δάσκαρις
), emperor of Nicaea (A. D. 1259-1261), was the son of the second emperor of Nicaea, Theodore II., Lascaris, whom he succeeded in 1259, at nine years of age.
He first reigned under the guardianship of the patriarch Arsenius and the Magnus Domesticus Muzalon.
The latter was slain, with his adherent, in a revolt of the guards, kindled by Michael Palaeologus, who was proclaimed emperor; and after having taken Constantinople from the Latins, in 1261, he deprived the youthful emperor of his eyes, and sent him into exile, where he died in obscurity. [MICHAEL VIII.]