The Intercolonial Railway of Canada (reporting mark IRC), also referred to as the Intercolonial Railway (ICR), was a historic Canadian railway that operated from 1872 to 1918, when it became part of Canadian National Railways. As the railway was also completely owned and controlled by the Government of Canada, the Intercolonial was also one of Canada's first Crown corporations.

The idea of a railway connecting Britain's North American colonies arose as soon as the railway age began in the 1830s. In the decades following the War of 1812 and ever-mindful of the issue of security, the colonies of Upper and Lower Canada (later the Province of Canada after 1840) wished to improve land-based transportation with the Atlantic coast colonies of Nova Scotia and New Brunswick, and to a lesser extent Prince Edward Island and Newfoundland. A railway connection from the Province of Canada to the British colonies on the coast would serve a vital military purpose during the winter months when the waters of the Gulf of St. Lawrence and St. Lawrence River were frozen and shipping was impossible, but it would similarly serve an economic purpose for the Maritimes by opening up year-round access to new markets.

Significant surveys were conducted throughout the 1830s–1850s. Several rival routes emerged: a southern, a central, and a northern route. In 1849, Major William Robinson recommended the northern route as most secure from American attack. Funding talks were established between the various colonial administrations and the British government, but progress remained slow and little was accomplished beyond talk.

Railway construction came to the Maritime provinces as early as the mid-1830s with the opening of the Albion Railway, a coal mining railway in Nova Scotia's Pictou County and the second railway to open in British North America. Construction in the 1850s saw two important rail lines opened in the Maritimes to connect cities on the Atlantic coast with steamship routes in the Northumberland Strait and the Gulf of St. Lawrence:

An intercolonial rail system in the British North American colonies was never far from the minds of government and civic leaders and in an 1851 speech at a Mason's Hall in Halifax, local editor of the Novascotian, Joseph Howe spoke these words:

I am neither a prophet, nor the son of a prophet, yet I will venture to predict that in five years we shall make the journey hence to Quebec and Montreal, and home through Portland and St. John, by rail; and I believe that many in this room will live to hear the whistle of the steam engine in the passes of the Rocky Mountains, and to make the journey from Halifax to the Pacific in five or six days.

But a rail connection between the Maritime colonies and the Province of Canada was not to be for another quarter century. Central Canada's dominant railway player in the 1850s was the Grand Trunk Railway (GTR) and its profit-driven business model chose the U.S. Atlantic port of Portland, Maine, over a much longer journey to a Maritime port. As a result, Portland boomed during the winter months when Montreal's shipping season was closed.

Nevertheless, the geopolitical instability in North America resulting from the American Civil War led to increased nervousness on the part of British North American colonies, particularly wary of the large Union Army operating south of their borders. The demands for closer political and economic ties between colonies led to further calls for an "Intercolonial Railway". An 1862 conference in Quebec City led to an agreement on financing the railway with the Maritime colonies and Canada splitting construction costs and Britain assuming any debts, but the deal fell through within months.^{[citation needed]}