[4][5] Ranau is noted for its hilly geographical structure and is the largest producer of highland vegetables in the state of Sabah.

Wang Dayuan mentioned a mountain called Long shan when he described the country of Bo ni (勃泥 bó ní) in his book, Description of the Barbarians of the Isles (島夷誌略 dǎo yí zhì lüè) written between 1330 and 1350.

[14][15] Another Chinese source, a nautical compendium called Fair Winds for Escort (順風相送 shùn fēng xiāng sòng) composed circa 1430, described a voyage from Siam to Mindanao via the west coast of Borneo, where the Chinese ships passed Sheng shan (聖山 shèng shān).

[18] The Dusun word ranahon (ranau) is used to describe a wet field of lowland rice and it was plausible that floods had submerged the plain, thus giving a lake-like view when seen from the highlands.

[18][31] During the British North Borneo Company administration beginning in the 19th century, Ranau was governed under the Province Dent.

[33] The Ranau plain and its surrounding hilly areas were historically inhabited by Dusun farmers who practised shifting cultivation.

[34] Tobacco, a major export item for the company,[35] was successfully cultivated in extensive parts of Ranau district, especially in the highlands.

[36] Between 1897 and 1898, Mat Salleh built a fort in Ranau and went there three times during his rebellion against the British North Borneo Company.

The company was aware of this development and launched an attack against his fort in Ranau on 23 February which led to the death of his father.

A total of 288 Sikh, Iban and Dayak policemen from Abai Bay and Sandakan led by G. Hewett, George Ormsby, P. Wise, and Adjutant Alfred Jones, were ordered to invade Mat Salleh's fort in Ranau on 13 December 1897.

On 9 January 1898, Hewett and his troops ambushed the Ranau fort again but it was already deserted by Mat Salleh and his followers.

[41] Ranau was under the Governorate of the West Coast Territory (西海州 seikaishū) and was directly administered by a district officer (郡長 guncho) with the help of village headmen.

[41] The Japanese set up a garrison in Ranau to control the local people and it was one of the strongest army posts in the Interior.

Another four prisoners successfully fled the camp and led to safety by a native teenager who found them hiding in the jungle along a river.

In June 1945, the Japanese captors moved with the prisoners 8.3 km (5.2 mi) south of Ranau to a second jungle camp near the Kenipir River to escape from the air raids of napalm bombs by the Allied planes.

[48] The Last Camp Memorial was newly unveiled in 2009 in remembrance of the exact spot where the Death March ended.

During the 25 years of operation, the Mamut Copper Mine was responsible for 50% of the gold and 90% of the silver production in Malaysia.

Filled with water, the crater now forms a huge lake, which - together with the heavy metal legacies of the Lohan Tailings Dam - made the headlines of several reports on environmental contamination.

On 5 June 2015, an earthquake measuring at 6.0 on the Richter magnitude scale occurred at 7:15 a.m. MST with its epicentre approximately 15 km north of Ranau.

[50][51] Mount Kinabalu was closest to the epicentre and was affected by massive landslides causing eighteen people to lose their lives, three of which were from Ranau.

[57] The northern part of Ranau is bounded by the Crocker Range and the Pinousok summit which runs in a southwesterly direction, to the east lies the Ranau plain and Trus Madi Range while the southern part is bounded by the Labuk highlands.

The racial makeup of the district consisted of 93.1% Kadazan-Dusun, 1.7% Chinese, 1.16% Bajau, 1.0% Malay, 0.15% Murut, 0.1% Indians, 4% Other Bumiputera and 0.8% listed as Others.

[5] 6.0% were Non-Malaysian citizens, mainly foreign workers from Indonesia and the Philippines working as labours in large farms and plantations.

Ranau is an important agricultural and tourism centre in Sabah and this two sectors have been the main economy backbone for the district.

The MARA Junior Science College (MRSM) Ranau campus admitted its first batch of students in March 2024.

Ranau commands a special place in the minds of all Kadazan-Dusun because of the significance of Nunuk Ragang as the original home of their ancestors, before the dispersal and migration throughout Borneo.

A landmark building in the form of a banyan tree has been built at the supposed site of the longhouse housing the first Kadazan-Dusun settlers of Nunuk Ragang.

Some Bobolians, keepers of the cultural and racial memories, opined that the ancestors came from "pogun Sina" or China Homeland.