A Deputy Prime Minister or Vice Prime Minister is, in some countries, a government minister who can take the position of acting Prime Minister when the Prime Minister is temporarily absent. The position is often likened to that of a vice president, but is significantly different, though both positions are "number two" offices. The position of Deputy Prime Minister should not be confused with the Canadian office of the Deputy Minister of the Prime Minister of Canada, which is a non-political civil servant position. The states of Australia and provinces of Canada each have the analogous office of Deputy Premier.

Deputy Prime Ministers traditionally serve as acting Prime Minister when the real Prime Minister is temporarily absent or incapable of exercising his/her power. For this reason the Deputy PM is often asked to succeed to the Prime Minister's office following the PM's sudden death or unexpected resignation, although this is not necessarily constitutionally mandated.

Deputy Prime Minister is often a job that is held simultaneously with another ministry, and is usually given to one of the most senior, experienced ministers of the cabinet.

A Deputy Prime Minister may also be Deputy Leader of the governing party.