Mainalo (Greek: Μαίναλο, Ancient Greek: Μαίναλος or Μαίναλον, romanized: Mainalos or Mainalon; Latin: Maenalus) is the tallest mountain in the Menalon highlands of the Peloponnese, and is located in Arcadia, Greece. In antiquity, the mountain was especially sacred to Pan.

The mountain's highest point, known as both Profitis Ilias and Ostrakina, at a height of 1,981 m (6,499 ft), is the highest point in Arcadia. The mountain has a length of 15 to 20 kilometres (9.3 to 12.4 mi) from southwest of Tripoli to northeast of Vytina, and a width of 5 to 10 kilometres (3.1 to 6.2 mi) from Zygovisti to Kapsas. The mountain is part of a Natura 2000 site, designated in March 2011, covering an area of 226.4 square kilometres (87.4 sq mi). In the 19th and early 20th century, the mountain was known as Apano Chrepa.

The mountain takes its name from the ancient Mount Mainalos, which was however located about 25 kilometers further south near the town of Asea, and has been identified as the same mountain known today as Ágios Ilías. The name was mistakenly connected to the current mounaint Mainalo by early European travelers. In Greek mythology, Mount Mainalos got its name from Maenalus, son of Lykaon, king of Arcadia.

Mainalo is home to a ski resort, which is found at an elevation of 1,600 metres (5,200 ft), with 7 ski slopes and 4 lifts, which are at an altitude between 1,550 to 1,770 metres (5,090 to 5,810 ft).

Mainalo's ground is primarily made of lime, among various calcareous substrates.

Mainalo has various named peaks. Listed by height, they are, among others;

• Ostrakina (Greek: Οστρακίνα) or Profitis Ilias (Greek: Προφήτης Ηλιας) at 1,981 metres (6,499 ft)
• Pateritsa (Greek: Πατερίτσα) at 1,875 metres (6,152 ft)
• Aidini (Greek: Αϊδίνη) at 1,849 metres (6,066 ft)
• Mavri Koryfi (Greek: Μαύρη Κορυφή) at 1,818 metres (5,965 ft)
• Mourtzia (Greek: Μουρτζιά) at 1,794 metres (5,886 ft)
• Mesovouni (Greek: Μεσοβούνι) at 1,730 metres (5,680 ft)
• Krevatia (Greek: Κρεββάτια) at 1,563 metres (5,128 ft)
• Epano Chrepa (Greek: Επάνω χρέπα) at 1,559 metres (5,115 ft)
• Lioritsi (Greek: Λιορίτσι) at 1,155 metres (3,789 ft)
• Sterna (Greek: Στέρνα) at 1,071 metres (3,514 ft)

The mountain houses many forests of Greek fir and Crimean pine. Natura 2000 cites these forests as the "[Greek fir and Crimean pine's] best representation in Peloponnisos."

Mainalo has several ecological environments, comprising:

• Mediterranean arborescent matorrals, covering 8.96 square kilometres (3.46 sq mi) of the mountain, this environment consists of Mediterranean and sub-Mediterranean sclerophyllous evergreen shrublands grouped under arborescent junipers.
• Endemic oro-Mediterranean heaths with gorse, covering 5.57 square kilometres (2.15 sq mi) of the mountain, this environment consists of a dry mountainous environment. Mediterranean heaths are usually dominated by Genista, while containing various other, often spined, shrubs like Acantholimon, Astragalus, Erinacea, Bupleurum, Ptilotrichum, Echinospartum, and Anthyllis. This environment also includes a variety of Asteraceae and Lamiaceae.
• Calcareous rocky slopes with chasmophytic vegetation, covering 0.22 square kilometres (0.085 sq mi) of the mountain, this environment consists of limestone cliffs and screes, featuring great ecological diversity, with many endemic plants growing in fissures within rock.

Many amphibians, reptiles, mammals, insects, and diurnal predatory birds inhabit Mainalo. These include, among others;

• Reptiles such as the Balkan whip snake, marginated tortoise, Kotschy's gecko, Greek rock lizard, Peloponnese wall lizard, European copper skink, and the horned viper.
• Mammals such as the European hare, beech marten, European badger, lesser noctule bat, edible dormouse, Thomas's pine vole, and the western broad-toothed field mice.
• Amphibians such as the European green toad, European tree frog, and the Syrian spadefoot.
• Birds such as the northern goshawk, Eurasian sparrowhawk, common buzzard, common kestrel, and the peregrine falcon.
• Insects such as the Kretania sephirus butterfly, Persian skipper butterfly, eastern orange tip butterfly and the mountain small white butterfly.

The following people were associated with the ancient city Maenalus, which may have stood near the summit of Mainalo:

• Androsthenes of Maenalus, a pankratiast who won gold in the ancient Olympic Games in 420 and 416 BC.
• Damoxenidas of Maenalus, a boxer who won gold in the ancient Olympic Games in 384 BC.
• Ephotion of Maenalus, a pankratiast who won gold in the ancient Olympic Games in 464 BC.
• Euthymenes of Maenalus, a boys' and adult wrestler who won gold in the ancient Olympic Games in 400 and 392 BC.
• Nicodamus of Maenalus, a sculptor who made statues of ancient Olympic victors and Greek mythological figures.
• Phormis of Maenalus, a distinguished fighter who became rich in service of Gelo.
• Xenocles of Maenalus, a boys' wrestler who won gold in the ancient Olympic Games in 372 BC.

Media related to Mainalo at Wikimedia Commons

• Mainalo Ski Center (in Greek)
• Forecasts on Mainalo
• University of Patras article on Mainalo and the Menalon highlands (in Greek)