Responsible government is a conception of a system of government that embodies the principle of parliamentary accountability, the foundation of the Westminster system of parliamentary democracy. Governments (the equivalent of the executive branch) in Westminster democracies are responsible to parliament rather than to the monarch, or, in a colonial context, to the imperial government, and in a republican context, to the president, either in full or in part. If the parliament is bicameral, then the government is usually responsible first to the parliament's lower house, which is more representative than the upper house, as it usually has more members and they are always directly elected.

Responsible government and the principle of parliamentary accountability manifests itself in several ways. Firstly, ministers must account to parliament for their decisions and for the performance of their departments. This requirement to make announcements and to answer questions in parliament means that ministers must have the privileges of the floor, which are only granted to those who are members of parliament. Secondly, and most importantly, although ministers are officially appointed by the authority of the head of state and can theoretically be dismissed at the pleasure of the sovereign, they concurrently retain their office subject to their holding the confidence of the lower house of parliament. When the lower house has passed a motion of no confidence in the government, the government must ordinarily immediately resign or submit itself to the electorate in a new general election.

Lastly, the head of state is in turn required to effectuate their executive power only through these responsible ministers. They must never attempt to set up a shadow government of executives or advisors and attempt to use them as instruments of government, or to rely upon their unofficial advice. They generally are not permitted to take any action under the color of their executive power without that action being as a result of the counsel and advisement of their responsible ministers. Common exceptions to this rule include emergency or wartime acts of necessity and the granting of certain state honours. Their ministers are required to counsel them (i.e., explain to them and be sure they understand any issue that they will be called upon to decide) and to form and have recommendations for them (i.e., their advice or advisement) to choose from, which are the ministers' formal, reasoned recommendations as to what course of action should be taken.

From the middle of the 19th century, the United Kingdom began to introduce systems of responsible government to the colonial governments of its settler colonies including in Canada, Newfoundland, Australia, New Zealand and South Africa. These systems were strongly based upon the system that had historically developed in the United Kingdom, with a bicameral legislature and an executive responsible to the Lower House.

Responsible government was implemented in several colonies of British North America (present day Canada), between 1848 and 1850, with the executive council formulating policy with the assistance of the legislative branch, which voted approval or disapproval, and the appointed governor enacting those policies that the legislature had approved. This replaced the previous system, whereby the governor took advice from an executive council and used the legislature chiefly to raise money.

Under responsible government, the executive is also a part of the legislature. The Executive branch must consist of MPs. Responsible government was a major element of Canada's gradual development toward independence. The concept of responsible government is associated in Canada more with self-government than with parliamentary accountability; hence, there is the notion that the Dominion of Newfoundland "gave up responsible government" when it suspended its self-governing status in 1933, as a result of financial problems. It did not regain responsible government until it became a province of Canada in 1949.

Following the formation of elected legislative assemblies, starting with Nova Scotia in 1758, governors and their executive councils did not require the consent of elected legislators in order to carry out all their roles. It was only in the decades leading up to Canadian Confederation in 1867 that the governing councils of those British North American colonies became responsible to the elected representatives of the people. In the aftermath of the American Revolution, sparked by the perceived shortcomings of virtual representation, the British government became more sensitive to unrest in its remaining colonies with large populations of European-descended colonists. Elected assemblies were introduced to both Upper Canada and Lower Canada with the Constitutional Act 1791. Many reformers thought that these assemblies should have some control over the executive power, leading to political unrest between the governors and assemblies in both Upper and Lower Canada. The Lieutenant Governor of Upper Canada, Sir Francis Bond Head, wrote in one dispatch to London that, if responsible government were implemented, "democracy, in the worst possible form, will prevail in our colonies."

After the Rebellions of 1837–1838 in the Canadas, the Earl of Durham was appointed governor general of British North America, with the task of examining the issues and determining how to defuse tensions. In his report, one of his recommendations was colonies that were developed enough should be granted "responsible government". This term specifically meant the policy that British-appointed governors should bow to the will of elected colonial assemblies.