The term federalist can refer to different ideologies, depending on the locale. It usually has a link, close or not, to the concept of a federation.

• In Europe a federalist is sometimes a proponent of:
  • Greater regional autonomy within a country (especially in states such as Switzerland and Belgium).
  • Greater integration, centralisation or supranationalism within the European Union.

• In Quebec, a federalist, in regards to the future of the Quebec people and the National Question, defends the concept of Quebec remaining within Canada, while either keeping the status quo or pursuing greater autonomy and national recognition for Quebec within the Canadian federation. This ideology is opposed to Quebec sovereigntism, proponent of Quebec independence, most often (but not for all followers) along with an economic union with Canada similar to the European Union.

• The United States the term federalist usually applies to a member of one of three groups:
  • Historically:
    • Statesmen and public figures supporting ratification of the proposed Constitution of the United States between 1787 and 1789. The Federalist Papers are documents associated with their movement.
    • Statesmen and public figures supporting the administrations of Presidents George Washington (1789–1797) and John Adams (1797–1801). Especially in the later years they are also called the Federalist Party.
  • In comtemporary usage, advocates of the principle of allowing greater regional autonomy within the United States — usually by allowing individual states to set their own agendas and determine the handling of issues, rather than trying to impose a 'national' solution. Usually federalism is proposed as a solution to issues that may have strong support in some parts of the country and strong opposition in other parts, for example: restrictions on abortion, gay marriage, euthanasia, medicinal use of cannabis, gun rights and restrictions on property rights.