Irkutsk Oblast (Russian: Ирку́тская о́бласть, romanized: Irkutskaya oblastʹ; Buryat: Эрхүү можо, romanized: Erkhüü mojo) is a federal subject of Russia (an oblast), located in southeastern Siberia in the basins of the Angara, Lena, and Nizhnyaya Tunguska Rivers.

It is drained by the Angara, which flows north across the province; the outflow rate is controlled by the Irkutsk Dam.

The two other major dams on the Irkutsk Oblast's section of the Angara are at Bratsk and Ust-Ilimsk; both forming large reservoirs.

The Lena has its source in Irkutsk Oblast as well, and flows north-east into the neighboring Sakha Republic.

By the end of the 17th century, Irkutsk had become a small town, monasteries were being built, and suburbs and agricultural settlements had started to form.

As the Russian state expanded to the east of Irkutsk, the city became the capital of enormous territories from the Yenisey River to the Pacific Ocean, and played an important role in the exploration and securing of vast Eastern-Siberian and Far-Eastern territories for Russia.

Gradually, Irkutsk gained more importance as the main transportation- and trade-center of Eastern Siberia; it became a center of trade routes from Kamchatka, Chukotka, Yakutia to Mongolia, and China.

Grigorii Ivanovich Shelikhov, an outstanding seafarer, played an important role in controlling enormous spaces of the northern part of the Pacific Ocean.

During the 18th century, schools, professional-technical education colleges, science museums, libraries, theaters, and book-printers developed in Irkutsk.

The 1780s saw the opening of the second public library in provincial towns in Russia, as well as a regional museum and an amateur theater.

The Irkutsk Spassky church [ru] of 1706 (one of the oldest stone buildings in Eastern Siberia), the unique Irkutsk Krestovozdvizhenskaya church [ru] (1747), the "Prikaznaya izba" (order house), the first stone construction, and the Triumph gate were built.

The Irkutsk merchant class began to play a major role in the city's development.

Private residences, hospitals, orphanages, and schools were built, while significant funds went towards education and the development of science in the region.

The Irkutsk White House [ru], done in Russian classic style in 1800–1804, and the Moscow Triumphal Gates of Irkutsk [ru] – a monument of the nineteenth century, were built in honor of the tenth anniversary of Alexander I's reign.

In 1851, the first scientific organization in Eastern Siberia – the Siberian branch of Russian geographical society, was opened.

V.I.Dybovskii, A.L.Chekanovskii, I.D.Cherskii, V.A.Obruchev, geologists, geographers and researchers of Siberia, worked in Irkutsk Oblast on exploring Lake Baikal and the Lena River.

Z. Muravyov, P. A. Mukhanov, A. P. Yushnevsky, V. A. Bechasnov, the wife of Trubetskoy and their children stayed in Irkutsk for the rest of their lives.

The Irkutsk Regional museum was stamped with the names of Siberian researchers on its walls (1883), the building of the first public community, city theater (1897), Kazan' cathedral, made in new Byzantine style (1893), and the Roman Catholic cathedral (1895) completed an architectural style of the city.

The city was damaged and influenced by the political events of the twentieth century – the Russian revolution, the 1917 October Revolution, the Civil war and the Great Patriotic War (as the Soviet Union's part in WW2 is commonly referred to in Russia.

At right is the Irkutsk orphanage named for E. Medvednikova, which served both as an eleemosynary institution and educational facility.

After the abolition of Article 6 of the Constitution of the USSR in March 1990, the CPSU lost its monopoly on power.

The head of the Oblast administration, and eventually the governor was appointed/elected alongside elected regional parliament.

The highest executive body is the Oblast Government, which includes territorial executive bodies such as district administrations, committees, and commissions that facilitate development and run the day to day matters of the province.

[18] One small ethnic group, concentrated in three villages (Pikhtinsk, Sredne-Pikhtinsk, and Dagnik) in Zalarinsky District is the so-called "Bug Hollanders": descendants of Polish-speaking Lutheran farmers who had moved to Siberia from the then Russian Volhynia in 1911–1912 in search of affordable land.

[citation needed] Although they had long lost German (or Dutch) language of their ancestors (even in the early twentieth century they spoke Ukrainian and read Polish), they were still considered ethnic Germans, and during World War II were usually drafted for work in labor camps, instead of front-line military service.

In addition, 37% of the population declares to be "spiritual but not religious", 17% is atheist, and 1.9% follows other religions or did not give an answer to the question.