ETYM Cf. French fédéraliste.
An advocate of federalism.

A member of a former political party in the US that favored a strong centralized federal government.
In Australian history, one who supported the federation of the six self-governing colonies into the Commonwealth of Australia which occurred on 1 Jan 1901.
In US history, one who advocated the ratification of the US Constitution 1787–88 in place of the Articles of Confederation. The Federalists became in effect the ruling political party during the presidencies of George Washington and John Adams 1789–1801, legislating to strengthen the authority of the newly created federal government.
The Federalists advocated reconciliation with Britain and were urban, educated, and vaguely antidemocratic.