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 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 of parliamentary accountability manifests itself in several ways. Ministers 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 either house 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 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 are bound to take no decision or action that is put into effect under the colour of their executive power without that action being as a result of the counsel and advisement of their responsible ministers. 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.