• Althaea (mythology), the daughter of Thestius and mother of Meleager
• Althaea (genus), a genus of about 12 species of perennial herbs, native to Europe and western Asia, that includes the marshmallow plant
• 119 Althaea, an asteroid

Furthermore,

• Althea, a variation of the Greek name, is an English female first name
• Altea is a town in Spain
• Althaea is also the name of several nymphs in Greek mythology
• "Rose of Althea" is another name for Hibiscus syriacus
• "Althea" is a Grateful Dead song

Althaea is the Latin rendering of Greek Ἀλθαία Althaia, which may be related to Greek ἀλθος althos "healing"