In the fictional Bleach manga/anime universe, a Hollow (虚（ホロウ）, Horō) is a type of monstrous lost soul who can harm both ghosts and humans. Many of the series' antagonists are hollows. Some hollows possess the characteristics called Arrancars (破面（アランカル）, Arankaru, from Spanish arrancar "to tear off," kanji translates as "broken mask") that are similar to those of a Soul Reaper (a death-related entity). One of the series' main storylines has Sōsuke Aizen (the primary antagonist for the majority of the series) and his arrancar (particularly the ten strongest Espadas) as the force opposing the protagonists.
The creator of the series, Tite Kubo, used many Spanish motifs for the series' hollow-related elements. The fictional creatures have been praised by reviewers for the early hollows' strong emotional ties to their victims and the "interesting" concept of the arrancar. The visual appearance of the characters has also been commented on.