Lysithea can refer to a few different things:

• Lysithea (alga), a genus of red algae in the family Bangiaceae
• Lysithea (moon), a moon of Jupiter
• Lysithea (mythology), a figure in Greek mythology
• Lysithea, a fictional spacecraft carrier in Voices of a Distant Star
• Lysithea von Ordelia, a fictional character from the video game Fire Emblem: Three Houses

• Cosmopterix lysithea, a species of moth