Mount Arapiles is a rock formation that rises about 140 metres (460 ft) above the Wimmera plains in western Victoria, Australia. It is located in Arapiles approximately 10 kilometres (6.2 mi) west of the town of Natimuk and is part of the Mount Arapiles-Tooan State Park. Arapiles is a very popular destination for rock climbers due to the quantity and quality of climbs. It is one of the premier climbing sites in Australia along with the nearby Grampians. The Wotjobaluk name for the formation is Djurid.

The Djurid Baluk clan of the Wotjobaluk people inhabited the nearby area for thousands of years prior to the European colonisation of Australia. They used the mountain's hard sandstone for making various stone tools, and found shelter in its many gullies and small caves. As with many groups affected by Australia's policy of Assimilation, the Djurid Balud were displaced from the area following European settlement in the mid-1840s, leading to the breaking up of the clan. The loss of the resources that the mountain provided, the ravages of European disease, and armed clashes with the settlers were all contributing factors. By the early 1870s, the last of the Djurid Balud had been relocated to mission stations. Some of their descendants still live in the area and there are also a number of archaeological sites nearby. Indeed, a survey of Mount Arapiles in 1992 located no fewer than 42 Aboriginal archaeological sites, including "quarries" for hard stone for implements, scarred trees and rock art sites.

The European colonisation of Australia also brought with it many explorers to chart the continent. The first recorded ascent of Arapiles was on 23 July 1836, by the European explorer, Major Thomas Mitchell. He named the landmark after the Arapiles hills near Salamanca, Spain, where the Battle of Salamanca took place, in which Mitchell had seen action.

An extract from Mitchell's diary on 22 July reads:

"This certainly was a remarkable portion of the earth's surface, and rather resembled that of the moon as seen through a telescope."

There is a plaque commemorating his contributions to Arapiles on the aptly named "Plaque Rock", which is close to the current campgrounds.

Mount Arapiles is primarily composed of quartzite, a metamorphic rock that was originally quartzose conglomerate and sandstone (quartz arenite). That protolith was laid down in the earliest part of the Devonian period (approx 420 Ma), as part of a substantial fluvial system. Evidence for that deposition can be seen in the decimeter-meter scale cross stratification and lateral accretion surfaces visible in the cliffs, and the presence of many beds containing well rounded, pebble size clasts. The nearby Grampians/Gariwerd mountain range contains some more distal facies of the same depositional system, which is evidenced by the lesser quantity of conglomerate and smaller average grain size.

Arapiles is preserved due to a granitic intrusion that was emplaced below the sandstone and conglomerate approx 400 Ma, or 20 million years after sedimentation. That intrusion advected heat from lower in the crust, facilitating pervasive quartz cementation of the detrital grains. The granite also contained some highly siliceous fluids that were driven off as the rock cooled. Those fluids probably also contributed to the cementation of the sediments. The process of direct heating due to magma transport is known as contact metamorphism.