Hydra is the second studio album by AmericanrockbandToto, released in 1979. It reached #37 on the Billboard Pop Albums. While most of the album's singles failed to make any impact in the charts, "99", a song inspired by the 1971 science fiction movie THX 1138, reached #26 on the Billboard Hot 100.
Though a commercial success, Hydra was far less popular than the band's top-selling debut. Allmusic suggested this was due to the band's failure to establish a distinctive, recognizable sound on either Hydra or their debut, which would have allowed listeners to immediately identify Toto's major hits with the band themselves. They also speculated that most listeners were not familiar with the film (namely, THX 1138) on which "99" was based, and thus found the lyrics hopelessly abstruse, preventing the song from becoming as big a hit as it could have been.
Critical response to the album was mixed. Allmusic's retrospective review made little judgment on the quality (noting only as an aside that the songs were "well-played"), instead discussing why it had failed to match the commercial success of their debut.