Alethea is an English-language female first name derived from the Ancient Greek feminine noun ἀλήθεια, alḗtheia, 'truth'.

Alethaire or Allethaire is possibly an Older Southern American English variant of Alethea that was in use by some Roman Catholic families in Kentucky by the 1700s.

[7] Increase in usage of the name coincided with a March 1973 guest appearance by 10-year-old child actress Jodie Foster in an episode of the American television series Kung Fu.

Variant spellings Alethia and Aletheia also increased in use in the United States for newborn girls between 1972 and 1973.

[11][13] Although the name has not appeared on popularity charts in other countries, it remains in occasional use worldwide.