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

• Althaea (mythology), the daughter of Thestius and mother of Meleager
• Althaea (plant), a genus of up to a dozen species of perennial herbs, native to Europe and western Asia, that includes the marshmallow plant
• 119 Althaea, an asteroid
• Althaea, the name of several nymphs in Greek mythology
• "Shrub Althea", "Shrub Althaea" and "Rose of Althea" are names applied to Hibiscus syriacus, which is South Korea's national flower

Althea, an English variation of the Greek name, may refer to:

• Althea, a female first name
• Althea, Missouri, a ghost town in the US
• Althea Racing, Italian-based motorcycle road racing
• EUFOR Althea, a European Union military operation in Bosnia and Herzegovina
• "Althea", a Grateful Dead song
• Althea, a fictional pulsar from the science-fiction novel The Hercules Text by Jack McDevitt
• Althea (1801 ship), a merchantman launched in 1802 at Calcutta that was wrecked in 1812
• U.S. Navy ships of the name include:
  • USS Althea (1862), a collier that served during the 1862
  • USS Althea (1863), a tugboat that served during the Civil War
  • USS Althea (SP-218), a motorboat built in 1907
• Althea (mesh network software), a mesh networking Linux software distribution based on OpenWRT

Altea, a Spanish variation of the Greek name, may refer to:

• Altea, a town in Spain