Isekai no Seikishi Monogatari (異世界の聖機師物語, lit. Sage Machine Master Story in the Different World), which was released in North America as Tenchi Muyo! War on Geminar, is a Japanese OVA series. It is a spin-off of the Tenchi Muyo! series, which was created by Masaki Kajishima. Produced by AIC Spirits and BeSTACK, the series aired thirteen episodes on pay-per-view network Animax between March 20, 2009 and March 19, 2010.

It chronicles the story of a young boy named Kenshi Masaki, the younger brother of Tenchi Muyo!'s protagonist Tenchi, who is transported to the world of Geminar. The story shares some character names and general terms from the anime Photon, another series created by Masaki Kajishima.

A light novel adaptation by Atsushi Wada was published by Fujimi Shobo on August 20, 2009 under their Fujimi Fantasia Bunko imprint. A manga adaptation was serialized in Comic REX and published by Ichijinsha on June 9, 2010, spanning two volumes. At Otakon 2012, Funimation Entertainment announced they had licensed the series for release in North America.The anime is part of the Tenchi Muyo! Ryo-Ohki continuity, taking place 15 years after the events of Tenchi Muyo! GXP.