In the history of the United States, carpetbagger is a largely historical pejorative used by Southerners to describe allegedly opportunistic or disruptive Northerners who came to the Southern states after the American Civil War and were perceived to be exploiting the local populace for their own financial, political, or social gain. The term broadly included both individuals who sought to promote Republican politics (including the right of African Americans to vote and hold office) and individuals who saw business and political opportunities because of the chaotic state of the local economies following the war. In practice, the term carpetbagger often was applied to any Northerners who were present in the South during the Reconstruction Era (1865–1877). The word is closely associated with scalawag, a similarly pejorative word used to describe white Southerners who supported the Republican Party-led Reconstruction.

White Southerners commonly denounced carpetbaggers collectively during the post-war years, fearing they would loot and plunder the defeated South and be allied politically with the Radical Republicans. Sixty men from the North, including educated free blacks and slaves who had escaped to the North and returned South after the war, were elected from the South as Republicans to Congress. The majority of Republican governors in the South during Reconstruction were from the North.

Since the end of the Reconstruction era, the term has been used to denote people who move into a new area for purely economic or political reasons despite not having ties to that place.

The term carpetbagger, used exclusively as a pejorative term, originated from the carpet bag, a form of cheap luggage, made from carpet fabric, which many of the newcomers carried. The term came to be associated with opportunism and exploitation by outsiders. It is now used in the United States to refer to a parachute candidate, that is, an outsider who runs for public office in an area without having lived there for more than a short time, or without having other significant community ties.

According to a 1912 book by Oliver Temple Perry, Tennessee Secretary of State and Radical Republican Andrew J. Fletcher "was one of the first, if not the very first, in the State to denounce the hordes of greedy office-seekers who came from the North in the rear of the army in the closing days of the [U.S. Civil] War", in the June 1867 stump speech that he delivered across Tennessee in support of the re-election of the disabled Tennessee Governor William G. Brownlow:

No one more gladly welcomes the Northern man who comes in all sincerity to make a home here, and to become one of our people, than I, but for the adventurer and the office-seeker who comes among us with one dirty shirt and a pair of dirty socks, in an old rusty carpet bag, and before his washing is done becomes a candidate for office, I have no welcome.

That was the origin of the term "carpet bag", and out of it grew the well known term "carpet-bag government".

In the United Kingdom at the end of the 20th century, carpetbagger developed another meaning, referring to people who joined a mutual organization, such as a building society, in order to force it to demutualize, that is, to convert into a joint stock company, seeking personal financial gain by that means.