The name Manitoba likely comes from the Cree words "Manitou bou," which mean "the narrows of the Great Spirit." The words applied to Lake Manitoba, which narrows to less than a kilometre at its centre. The waves hitting the loose surface rocks of its north shore produce curious bell-like and wailing sounds, which the first Aboriginal peoples believed came from a huge drum beaten by the spirit Manitou.

The Plains Ojibwa, Cree and Assiniboine tribes inhabited the prairies of what is now southern Manitoba. Culturally, they were related to Great Plains tribes living farther south. They were nomadic hunters whose complex culture was based primarily on the taking and processing of bison meat and hides. In the north, the population was more culturally akin to the Inuit people. They hunted caribou, fished and collected wild vegetables and berries in the summertime.

In their search for the rich Orient through the Northwest Passage, Europeans reached Manitoba through Hudson Bay. Unlike most of the rest of Canada, the northern parts of the province were settled before the south. A blot on the horizon; that is how Manitoba was originally described, a blockage in the way of the anticipated North West Passage. It was in this way that Manitoba was discovered in 1612 when Captain Button saw land on the horizon somewhere in the vicinity of present day Churchill.

Captain Button wintered two ships at the mouth of the Nelson River, on Hudson Bay. Later, a party led by La Vérendrye explored the Red and Winnipeg rivers in the years 1733-38 and built several outposts.

Early European interest in Manitoba centred on the fur trade. In 1670, the Hudson's Bay Company was created, and King Charles II of England granted it a large tract of land named Rupert's Land. The company set up fur-trading posts to exploit the country's wealth. During the 18th century, intense rivalry for fur-trade supremacy developed between the Montreal-based North West Company and the Hudson's Bay Company.

In 1812, the first European agricultural settlement was established in the area around the junction of the Red and Assiniboine rivers by Lord Selkirk, a Scottish nobleman who sent a number of Scottish Highlanders to settle land he had secured from the Hudson's Bay Company. He called the area Assiniboia. The Selkirk colony suffered through floods and problems arising from unfamiliarity with the environment and rivalries within the fur trade. Nevertheless, the settlement survived.

In 1836, Assiniboia was transferred to the Hudson's Bay Company by the Selkirk family. The Dominion of Canada was established in the 1860s, and the lands of the Hudson’s Bay Company were scheduled to become part of the new confederation. Negotiations for the transfer of sovereignty of the Hudson's Bay Company lands to Canada followed, but with little regard to the wishes of the inhabitants.

During the lengthy negotiations, this lack of consultation and the movement of American and Canadian settlers into the territory led the Métis (people of mixed Aboriginal and European blood) to fear for the preservation of their land rights and culture. The Métis, under the leadership of Louis Riel, opposed the Canadian proposals in an insurgency known as the Red River Rebellion. The uprising was eventually put down, but Riel succeeded in establishing a locally-elected, provisional government in December, 1869. Delegates of this provisional government negotiated terms with the new federal government of Canada, making Manitoba a province of the Dominion of Canada on July 15, 1870. (Riel, however, was later hanged for taking part in a rebellion in Saskatchewan.)

The new "postage stamp" province (so named because of its square shape and small size) consisted then of 36,000 km² surrounding the Red River Valley. However, the province did not remain that small; its boundaries were expanded in 1881 and again in 1912.

The appearance of the first railroads in the 1880s and the newcomers of many nationalities and cultures who rode them served to tie Manitoba even more closely to the rest of Canada. The railroads also raised its status as a breadbasket province that provided agricultural products to the nation. Even today, when manufacturing constitutes a good share of the province’s economy (especially in Winnipeg), Manitoba still depends greatly on wheat and cattle for its prosperity.

For many years, most Manitobans were of British origin. But changes in migration and immigration patterns have produced an ethnically diverse population. Manitoba is home to dozens of groups from all over the world, who have enriched the province's economy, culture and society. It boasts a significant Francophone community.

Although Manitoba is one of the smaller provinces in population, it is an important centre for a number of ethnic groups. It is one of the most important centres of Ukrainian culture outside Ukraine and has one of the largest populations of Mennonites in the world. More than 115,000 people are of Amerindian or Métis origin.

About 60 percent of Manitoba's 1,145,000 people live in metropolitan Winnipeg, the provincial capital. The second-largest city is Brandon, in southwestern Manitoba.