Althea (アルシア Arushia, lit. "Alcia") is a giant floating island kingdom ruled by Charles De Bergt Althea The 11th with Neue Welt as its royal capital. It was made by the instructors of 13th Special Military Forces School with Althing after the end of the Abandonment War 300 years ago. It is the main base of operations of Althea Royal Guard and Special Service.
- In Chapter 44, Althea's name was written as "Arusier", a German word.