The dissolution of a legislative assembly (or parliament) is the simultaneous termination of service of all of its members, in anticipation that a successive legislative assembly will reconvene later with possibly different members. In a democracy, the new assembly is chosen by a general election. Dissolution is distinct on the one hand from abolition of the assembly, and on the other hand from its adjournment or prorogation, or the ending of a legislative session, any of which begins a period of inactivity after which it is anticipated that the same members will reassemble. For example, the "second session of the fifth parliament" could be followed by the "third session of the fifth parliament" after a prorogation, but would be followed by the "first session of the sixth parliament" after a dissolution.

In most Continental European countries, dissolution does not have immediate effect – that is, a dissolution merely triggers an election, but the old assembly itself continues its existing term and its members remain in office until the new assembly convenes for the first time. In those systems, ordinarily scheduled elections are held before the assembly reaches the end of a fixed or maximum term, and do not require a dissolution.

In most Westminster systems, however, a dissolution legally ends the existence of the assembly, resulting in a temporary power vacuum, which may be filled in special circumstances by recalling the old assembly if need be.^{[citation needed]} Because of this peculiarity, Westminster systems also have automatically-triggered dissolutions when the assembly reaches the end of a fixed or maximum term, since the act of dissolution itself is synonymous with the end of the assembly's term, and elections cannot be held in anticipation of a dissolution.

Early dissolutions may be possible in parliamentary and semi-presidential systems, to resolve conflicts between the executive and the legislature; either a "snap election" called by an executive seeking to increase its legislative support, or an election triggered by parliament withholding confidence and supply from the government. Some presidential systems also allow early dissolutions, usually by the legislature voting to dissolve itself (as in Cyprus), but sometimes by executive action in more authoritarian presidential systems, or, as in Ecuador's muerte cruzada, the president dissolving the legislature at the cost of facing a new election themselves.

In a bicameral legislature, dissolution may apply jointly or separately to the lower house and upper house, or may apply only to the lower house, with the upper house never fully dissolved. In a bicameral Westminster system, the expression "dissolution of parliament" typically refers to the dissolution of the lower house, just as "member of parliament" means member of the lower house.

The House of Representatives, but not the Senate, can be dissolved at any time by the governor-general on the advice of the prime minister. The term of the House expires three years after its first meeting if not dissolved earlier. The governor-general can dissolve the Senate only by also dissolving the House of Representatives (a double dissolution) and only in limited circumstances spelled out in the Constitution.

There is a convention that the Governor-General only orders a dissolution on the advice of the prime minister. This convention was demonstrated in the dismissal of prime minister Gough Whitlam by Governor General Sir John Kerr in 1975. Kerr claimed that dissolving the House of Representatives was his duty and "the only democratic and constitutional solution" to the political deadlock over supply. Whitlam refused to advise Kerr to call an election, and Kerr replaced him with a caretaker prime minister, Malcolm Fraser. Fraser promptly advised a double dissolution, and Sir John acted in accordance with that advice.

Unlike the Commonwealth Parliament, the premier and governor of Victoria have very little discretion in dissolving the Parliament of Victoria. Both the Legislative Assembly and the Legislative Council are dissolved automatically twenty-five days before the last Saturday in November every four years. However, the governor can dissolve the Legislative Assembly if a motion of no confidence in the premier and the other ministers of state is passed and no motion of confidence is passed within the next week. Finally, the premier can advise the governor to dissolve both houses in the case of a deadlocked bill.