Skylan the Lepercentacorn's Page

 Senātus Populusque Rōmānus ("The Senate and People of Rome", see translation), referring to the government of the ancient Roman Republic, and used as an official emblem of the modern-day comune (municipality) of Rome. It appears on coins, at the end of documents made public by inscription in stone or metal, in dedications of monuments and public works, and was emblazoned on the standards of the Roman legions.

SPQR is an initialism from this Latin phrase