Tenchi Muyo! Ryo-Ohki (天地無用! 魎皇鬼, Tenchi Muyō! Ryōōki?) is a twenty episode collection of OVAs produced by AIC, initially released in Japan in 1992. The first two OVA series were later licensed and distributed in North America by Pioneer LDC, with FUNimation Entertainment taking over the rights for the third (and latest) series.

The distribution of the first OVA series was originally started in September 1992 and released six episodes that lasted until 1993. The first series was so successful that a seventh special episode was released in January 1994, followed by a Second OVA series with six additional episodes that begun distribution in September 1994 and lasted for one year until September 1995. However the Second OVA series ended on a cliffhanger and it wasn't until nearly eight years later in 2003 that a third OVA series was distributed in Japan. The third OVA series ended the Tenchi Muyo OVA storyline with six episodes, followed by a special episode released in September 2005 that concluded the storyline.

Source: Wikipedia