Ainis (Ancient Greek: Αἰνίς, IPA: [ajˈniːs], Modern Greek Αινίδα, IPA: [eˈniða]) or Aeniania (Αἰνιανία), was a region of ancient Greece located near Lamia in modern Central Greece, roughly corresponding to the upper valley of the Spercheios river.

[1] Ainis is located in the upper Spercheios valley, bordering with Dolopia in the west, Oitaia in the south, Malis in the east and Achaia Phthiotis in the north.

[1] The river Spercheios flows through the region on its way down to the Maliac Gulf, and is joined in Ainis by its chief tributary the Inachos.

After the introduction of modern heating, the previously bald foothills of the surrounding mountains are now covered with dense thickets of ivy and prickly pear.

12) that the Ainianians were once expelled from Thessaly by the Lapiths to wander the Greek peninsula until they finally settled in the upper Valley of Spercheios.

[1] A smaller settlement, that of Makra Kome, is also mentioned in a passage by Livy as being ravaged by the Aetolians during the Second Macedonian War.

An elongated hill near the village of Vitoli (Βίτολη) bears the name 'astrorachi (Καστρόραχη, "castle ridge"), and on its top there are remains of a wall with many towers as well as an impressive gate.

The strategic importance of the fortifications are not to be underestimated since the location dominates the upper plain of the valley as well as the confluence of the Spercheios with its tributary, the Papagourna.

[6] Located in the centre of ancient Ainis, the hill of Profitis Ilias (Προφήτης Ηλίας) overlooks most of the lower plains of the Spercheios and guards the pass of Giannitsou, leading north to Thessaly.

[6] In the foothills and at the plain below the hill, Georges Roux in 1954 noted remains of a possible lower city, as well as some epigraphical material in the nearby village of Platystomo.

The site at Profitis Ilias is currently the subject of an archaeological survey conducted by the 14th Ephorate at Lamia and the Swedish Institute at Athens.