"Undefeated Weakest Bahamut") is a Japanese light novel series, written by Senri Akatsuki and illustrated by Ayumu Kasuga and Yuichi Murakami.

The empire's former prince, Lux Arcadia, accidentally trespasses in a female-only bathing area, and witnesses the new kingdom's princess Lisesharte Atismata naked and her secret.

After a duel with Lisesharte, Lux attends the female-only academy where they train students to become royal Drag-Knights.

The first light novel volume was published on August 12, 2013, by SB Creative under their GA Bunko imprint.

"Wyvern Knight") by True, while the ending theme is "Lime Tree" (ライムツリー) by Nano Ripe.