He was born Sahle Miriam on August 17, 1884, in Ankober, Shewa, Ethiopia. His mother, Woizero Ejigayehu Lemma Adyamo, was a palace servant, and his father was Prince Haile-Melekot, Son of King Sahle Selassie. During an 1855 invasion by Emperor Tewodros II, Melekot was killed and Miriam was taken prisoner and held captive for ten years in the emperor’s mountain stronghold of Amba Magdala. He was raised alongside the Emperor’s children and treated as a prince.
In nearly 10 years of captivity, he had opportunity to observe Tewodros’s dedication to the unification and modernization of the empire and also the heavy-handed and often violent methods that ultimately led to the emperor’s failure and suicide.
Sahle Mariam contrived to escape from Magdela in 1865 and returned to Shewa, which had remained in a state of sporadic unrest and revolt against Tewodros. Although only 21 years of age, he was able to displace Bezebeh, who had been appointed ruler by the emperor in 1859, and subsequently declared himself negus of the province. Sahle Mariam stood six feet tall and had a dark complexion and fine white teeth, but smallpox had left its marks on his face.
Emperor Menelik II was a federalist that believed that the region would be strongest under a consolidated central Imperial crown at Addis Ababa (aka Addis Abeba or "new flower"), a location that would be chosen in 1886 by his Empress Taytu Betul, a city-state like London and Washington D.C. Menelik II's leadership efforts focused on consolidating the Ethiopian empire under royal patriarchal Imperial rule. During his reign, the British had heavily armed Emperor Yohannes IV (aka King John of Abyssinia) against Emperor Tewodros II.
By 1880, Menelik II was signing a treaty with the Italians in the Wollo province at Wuchale, acknowledging the establishment of the Italian colony of Eritrea and its capital at Asmara. Eritrea is in the northern Tigrean region. As a result, this treaty signing weakened the rule of Ras Mengesha, the son of the late Emperor Yohannes IV, over the region. When Menelik II signed the treaty with the Italians, he did not know that the Amharic version was different from the Italian version (Uccialli), a common trickery used by many European colonialists against native populations. When Menelik II discovered the deception, he denounced the Italian treaty. Italy declared war against Menelik II and invaded Ethiopia from Asmara.
Menelik II defeated the Italians at Amba-Alagi and Mekele. On March 1, 1896, Menelik II inflicted a decisive blow against Italian soldiers at the Battle of Adwa, forcing Italy to recognize Ethiopia's national sovereignty. Ras Mengesha was able to eventually secure Emperor Menelik II's recognition of his position as Prince of Tigray (aka Tigrai). Ras Mengesha had supported Menelik II's efforts to defeat the Italian invasion in 1896 in the Battle of Adwa. Menelik, however, refused to crown Ras Mengesha as King of Zion, which led to his rebellion against Menelik. In 1898, Menelik II defeated a rebellion by Ras Mangasha, further consolidating Imperial authority over Ethiopia, unifying the Ethiopian highlands. Ras Mengesha was defeated and placed under house arrest until his death.
The Ethiopian Empire was transformed under Emperor Menelik: the major signposts of modernisation were put in place, with the assistance of key ministerial advisors. Externally, Menelik led Ethiopian troops against Italian invaders in the First Italo-Ethiopian War; following a decisive victory at the Battle of Adwa, recognition of Ethiopia's independence by external powers was expressed in terms of diplomatic representation at his court and delineation of Ethiopia's boundaries with the adjacent colonies. Menelik expanded his realm to the south and east, into Oromo, Kaffa, Sidama, Wolayta and other kingdoms or republics.
Menelik II was fascinated by modernity, and like Tewodros II before him, he had a keen ambition to introduce Western technological and administrative advances into Ethiopia. Following the rush by the major powers to establish diplomatic relations following the Ethiopian victory at Adwa, more and more westerners began to travel to Ethiopia looking for trade, farming, hunting, and mineral exploration concessions. Menelik II founded the first modern bank in Ethiopia, the Bank of Abyssinia, introduced the first modern postal system, signed the agreement and initiated work that established the Addis Ababa –Djibouti railway with the French, introduced electricity to Addis Ababa, as well as the telephone, telegraph, the motor car, and modern plumbing. He attempted unsuccessfully to introduce coinage to replace the Maria Theresa thaler.
On 27 October 1909, Menelik II suffered a massive stroke and his "mind and spirit died". After that, Menelik was no longer able to reign, and the office was taken over by Empress Taytu, as de facto ruler, until Ras Bitwaddad Tesemma was publicly appointed regent. However, he died within a year, and a council of regency from which the empress was excluded was formed in March 1910.
In the early morning hours of 12 December 1913, Emperor Menelik II died. He was buried quickly without announcement or ceremony at the Se'el Bet Kidane Mehret Church, on the grounds of the Imperial Palace. In 1916 Menelik II was reburied in the specially built church at Ba'eta Le Mariam Monastery in Addis Ababa. After the death of Menelik II, the council of regency continued to rule Ethiopia. Lij Iyasu was never crowned Emperor of Ethiopia, and eventually, Empress Zewditu I succeeded Menelik II on 27 September 1916.