Semper Fidelis is a Latin motto translating to "always faithful". It is the motto of:

• Plymouth Argyle, and the song is played as the team enters the pitch before the start of the game.
• The City of Exeter, in Devon, England; the motto signifies the city's loyalty to the English Crown, and was suggested by Elizabeth I in a letter of 1588 to "The Citizens of Exeter", in recognition of a gift of money towards the fleet that defeated the Spanish Armada.
• The Galician city of Leopolis (now L'viv in Ukraine); the words were first used in 1658 by Pope Alexander VII recognizing the city's key role in defending Europe from a Muslim invasion; in the same year the Sejm of the Polish-Lithuanian Commonwealth passed the Semper fidelis poloniae Act (which is how most people understand it). Curiously, as well as having the same motto, both Exeter and Leopolis have a three-turreted castle on their coats of arms (see illustrations), but this is apparently no more than a coincidence. Today in Poland the phrase is used mainly in connection with the Polish-Ukrainian skirmishes after the fall of Austro-Hungary, and more particularly to the Polish-Bolshevik war. In Ukraine it is much less used, and refers to the survival of the Ukrainian Church through the period of Soviet persecution.
  • In the 1990s the words along with Mortui sunt ut liberi vivamus (Latin for They died for us to live free) were a subject of a Polish-Ukrainian controversy regarding the restoration of a Polish military cemetery desecrated by the Soviets in L'viv.
• HMS Exeter, a Royal Navy warship named after the City of Exeter.
• The United States Marine Corps, the amphibious infantry element of the United States Navy, who often reduce it to Semper Fi; the motto signifies the dedication that individual Marines are expected to have to "The Corps" and to their fellow fighting men and women, for the rest of their days and beyond.
• Semper Fidelis is the title of the official march of the United States Marine Corps, composed by John Phillip Sousa in 1889. Sousa was director of the United States Marine Corp Band when a replacement for Hail to the Chief was requested, but later rejected. Sousa considered it to be his "most musical" march.