Basiliscus (Latin: Flavius Basiliscus Augustus; Greek: Βασιλίσκος; d. 476/477) was Eastern Roman or Byzantine Emperor from 475 to 476. A member of the House of Leo, he came to power when Emperor Zeno was forced out of Constantinople by a revolt.
Basiliscus was the brother of Empress Aelia Verina, who was the wife of Emperor Leo I (457–474). His relationship with the Emperor allowed him to pursue a military career that, after minor initial successes, ended in 468, when he led the disastrous Roman invasion of Vandal Africa, in one of the largest military operations of Late Antiquity.
Basiliscus succeeded in seizing power in 475, exploiting the unpopularity of Emperor Zeno, the "barbarian" successor to Leo, and a plot organised by Verina that had caused Zeno to flee Constantinople. However, during his short rule, Basiliscus alienated the fundamental support of the Church and the people of Constantinople, promoting the Miaphysite christological position in opposition to the Chalcedonian faith. Also, his policy of securing his power through the appointment of loyal men to key roles antagonised many important figures in the imperial court, including his sister Verina. So, when Zeno tried to regain his empire, he found virtually no opposition, triumphantly entering Constantinople, and capturing and killing Basiliscus and his family.
The struggle between Basiliscus and Zeno impeded the Eastern Roman Empire's ability to intervene in the fall of the Western Roman Empire, which happened in early September 476. When the chieftain of the Heruli, Odoacer, deposed Western Emperor Romulus Augustus, sending the imperial regalia to Constantinople, Zeno had just regained his throne, and he could only appoint Odoacer dux of Italy, thereby ending the Western Roman Empire.