Abu-Hassan  (ā-bö-has ´an ).—As related in the Arabian Nights, Abou Hassan is a merchant of Bagdad who is carried in his sleep to the bed of the Caliph Haroun-al-Raschid and on awaking is made to believe himself the caliph. Twice in this way he was made to believe himself caliph and afterward became in reality the caliph's favorite and companion.