The Ondine Knights are a Tristain army corps consisting of male students of the Tristanian Academy of Magic. Saito was initially considered for the position of Captain but a number of issues prevented him from taking the command, and so the position went to Guiche due to his own military background and exploits during the war in Albion. Their 'headquarters' consists of a wooden house on the grounds of the Academy. The Knights take part in a series of events in both Tristain, Gallia, and Romalia throughout both the manga and light novel.
- Guiche de Gramont (Captain)
- Chevalier Hiraga Saito (Lieutenant)
- Malicorne de Grandpre
- Adrian, Alsenu, Guston, Varantun, Victor, Paul, Ernesto, Oscar, Gazmeal
- Despite being referred to as a 'Corps', most modern army corps contain 20,000-40,000 troops all under the command of a Lieutenant General. As they are an order of students numbering only 100 or so under the command of a Captain the Knights of Ondine are more of a Company.
- Their full name, as mentioned in the Light Novel, is 'The Ondine Knight Corps of the Water Spirit'. The water spirit in question is a legendary being that supposedly granted the Tristain Royal family their water magic.