Italian East Africa (Italian: Africa Orientale Italiana, A.O.I.) was a colonial possession of Fascist Italy from 1936 to 1941 in the Horn of Africa. It was established following the Second Italo-Ethiopian War, which led to the military occupation of the Ethiopian Empire (Abyssinia). It encompassed Italian Somaliland, Italian Eritrea and the acquired Ethiopian territories, all governed by a single administrative unit, the Governo Generale dell'Africa Orientale Italiana. Its establishment contributed significantly to the outbreak of the Second World War by exposing the weaknesses of the League of Nations.

Italian East Africa was divided into six governorates. Eritrea and Somalia, Italian possessions since the 1880s, were enlarged with captured Ethiopian territory and became the Eritrea and Somalia Governorates. The remainder of the occupied Ethiopian territories comprised the Harar, Galla-Sidamo, Amhara, and Scioa Governorates. At its largest extent, Italian East Africa occupied territories in British Somaliland, British Kenya, and Anglo-Egyptian Sudan. By 1939, it was settled by about 165,270 Italian colonists.

During World War II, Italian East Africa became the battleground of the East African campaign (part of the Mediterranean and Middle East theater). After the Battle of Gondar in November 1941, it was occupied by a British-led force including colonial units and Ethiopian resistance fighters. All former Italian territories came under British administration; occupied Ethiopia was ruled until full sovereignty was restored in 1944. In 1950, Allied occupied Somalia became the United Nations Trust Territory of Somaliland, administered by Italy from 1950 until its independence in 1960. Allied occupied Eritrea became an autonomous part of Ethiopia in 1952. It was later annexed by the Ethiopian Empire in 1962 and gained its independence in 1993 as Eritrea.

In the late 19th and early 20th centuries, Italy sought to expand its colonial empire, competing with other European powers for overseas territories. Early efforts included the colonization of Eritrea (1890) and Italian Somaliland (1905), followed by the unsuccessful invasion of the Ethiopian Empire in the First Italo-Ethiopian War (1895–1896). After World War I, nationalist sentiments grew, fueled by the belief that Italy had been denied its rightful territorial rewards for its contribution to the war effort, a sentiment known as the Mutilated Victory (Italian: Vittoria Mutilata). The combination of mobilization costs and the social unrest that followed the war is widely thought to have strengthened Italian irredentism and nationalism. This frustration contributed to the rise of Benito Mussolini and his Fascist regime in 1922.

Mussolini injected a new and aggressive impetus into these frustrations and ambitions, framing colonial expansion as a means to restore Roman greatness, enhance national prestige, and solve Italy's economic problems by providing land and resources. Mussolini believed the Italian people lacked a strong nationalistic and colonial conscience and thus sought to cultivate these sentiments through Fascist propaganda, particularly in the lead-up to the invasion and during occupation of the Ethiopia Empire. This propaganda emphasized Italy's need for colonial territories (Italian: spazio vitale), the perceived danger of Ethiopian aggression, and the injustice of international opposition to Italian expansion. The conquest of Ethiopia in 1936 and the subsequent formation of Italian East Africa were presented as major achievements of the Fascist regime, aimed at fulfilling long-standing Italian ambitions and establishing Italy as a major power. Despite earlier consideration of a protectorate over parts of Ethiopia, the Fascist government pursued full conquest, driven by Mussolini's determination to achieve a significant colonial victory to bolster his regime's legitimacy and international standing. This ambition, however, was met with Ethiopian resistance and international complications. This further aligned Italy with Nazi Germany, setting the stage for its involvement in World War II.

The Italo-Ethiopian Treaty of 1928 stated that the border between Italian Somaliland and Ethiopia was 21 leagues parallel to the Benadir coast. In 1934, a border clash at Ual-Ual between Italian and Ethiopian forces during a boundary survey provided Mussolini with a pretext for a war. The Second Italo-Ethiopian War began without prior declaration of war in October 1935, with Italy sending a modern army of two hundred thousand soldiers commanded by Marshal Emilio De Bono and General Rodolfo Graziani (and later Pietro Badoglio). This army was equipped with superior weaponry, including an air force and tanks. Italian troops used mustard gas in aerial bombardments (in violation of the Geneva Protocol and Geneva Conventions) against combatants and civilians in an attempt to discourage the Ethiopian people from supporting the resistance. This military superiority over the Ethiopian army, combined with the then Ethiopian Emperor Haile Selassie's initial strategy of engaging in frontal battles led to significant Italian victories. During the late stages of the war, Italian forces violated international agreements by bombing Red Cross ambulances and hospitals, claiming these actions were in retaliation for alleged Ethiopian atrocities.

While some Italians initially opposed the war due to fears of a broader European conflict and Italy's financial instability, the Italian public largely shifted to support Mussolini following reported victories. Selassie was forced to flee to England, with Italian forces entering the capital city, Addis Ababa by 5 May 1936. Shortly after, Mussolini proclaimed an "Italian Empire of Ethiopia" and the Italian Empire on May 9, 1936. Following the Italian conquest, Ethiopian patriotic resistance continued in various parts of the country, particularly in the north and northwest. The resistance, although facing the challenge of Italy's modern military and harsh reprisals, prevented Italy from fully controlling Ethiopia and hindered its plans for economic and demographic exploitation. This ongoing opposition set the stage for Ethiopia's eventual involvement in the Second World War.

Since 28 September 1923, the Ethiopian Empire had been one of the member states of the League of Nations after its membership was supported by Mussolini. Following Italy's invasion, the League imposed economic sanctions on Italy, restricting trade in arms, rubber, and certain raw materials. However, the sanctions did not include oil, which was needed for Italy's war effort. France and Britain, concerned about maintaining good relations with Italy against the growing German threat, hesitated to enforce harsher penalties (appeasement). In 1936, the League lifted the sanctions, effectively legitimizing Italy's conquest. The failure of the League to protect the Ethiopian Empire exposed its weaknesses, demonstrating its inability to deter aggression from major powers. This failure was a key moment in the lead-up to World War II, undermining the League's credibility as a force for global peace. Although Selassie fled to England and appealed to the League of Nations for help, many nations gradually recognized the Italian annexation for political and economic reasons. On 18 November 1936, the Italian Empire was recognised by the Empire of Japan and Italy recognised the Japanese occupation of Manchuria, marking the end of the Stresa Front. Mussolini's international popularity further decreased as he endorsed the annexation of Austria by Nazi Germany, beginning a political tilt toward Germany that eventually led to the downfall of Mussolini and the Fascist regime in Italy in World War II.