Phthia (Greek: Φθίη Transliterations:, Modern: Fthii, Ancient: Phthiē) is an ancient region of Greece, at the southern part of Magnesia, on the both sides of Othrys mountain. It was the homeland of the Myrmidones tribe, who took part in the Trojan War under Achilles.

Founded by the grandfather of Achilles and was the home of his father Peleus and his sea-nymph mother Thetis.

See also

• Fthiotis

189 Phthia is an asteroid.