In the process of setting electoral districts, gerrymandering is a practice that attempts to establish a political advantage for a particular party or group by manipulating geographic boundaries to create partisan or incumbent-protected districts. The resulting district is known as a gerrymander ( /ˈdʒɛriˌmændər/); however, that word can also refer to the process.

Gerrymandering may be used to achieve desired electoral results for a particular party, or may be used to help or hinder a particular demographic, such as a political, racial, linguistic, religious or class group.

When used to allege that a given party is gaining disproportionate power, the term gerrymandering has negative connotations. However, a gerrymander may also be used for purposes that some perceive as positive, such as in US federal voting district boundaries that produce a majority of constituents representative of African-American or other racial minorities (these are thus called "majority-minority districts").

Gerrymandering should not be confused with malapportionment, whereby the number of eligible voters per elected representative can vary widely without relation to how the boundaries are drawn. Nevertheless the ~mander suffix has been applied to particular malapportionments, such as the "Playmander" in South Australia and the "Bjelkemander" in Queensland. Sometimes political representatives use both gerrymandering and malapportionment to try to maintain power.^{[citation needed]}