A safe seat is an electoral district (constituency) in a legislative body (e.g. Congress, Parliament, City Council) which is regarded as fully secure, for either a certain political party, or the incumbent representative personally or a combination of both. With such seats, there is very little chance of a seat changing hands because of the political leanings of the electorate in the constituency concerned and/or the popularity of the incumbent member. The opposite (i.e. more competitive) type of seat is a marginal seat. The phrase tantamount to election is often used to describe winning the dominant party's nomination for a safe seat.
There is a spectrum between safe and marginal seats. Safe seats can still change hands in a landslide election, such as Enfield Southgate being lost by the Conservatives (and potential future party leader Michael Portillo) to Labour at the 1997 UK general election, whilst other seats may remain marginal despite large national swings, such as Gedling, which Labour narrowly won in every election for twenty years until the 2019 general election, despite having both major victories and defeats during this time. Gedling would still be seen as a marginal seat, even though it had been held by Labour for a long time. Safe seats are usually seats that have been held by one party for a long time, but the two concepts are not interchangeable.
In countries with parliamentary government, parties often try to ensure that their most talented or influential politicians are selected to contest these seats – in part to ensure that these politicians can stay in parliament, regardless of the specific election result, and that they can concentrate on ministerial roles without needing to spend too much effort on managing electorate-specific issues.
Candidate selection for a party's safe seats is usually keenly contested, although many parties restrict or forbid challenges to the nomination of sitting members.