Salus populi suprema lex esto (Latin "The health of the people should be the supreme law," "Let the good (or safety) of the people be the supreme (or highest) law" or "The welfare of the people shall be the supreme law") is a maxim or principle found in Cicero's De Legibus (book III, part III, sub. VIII)
The phrase is the state motto of Missouri, accepted, like many other states, as an element of its state seal. It is also the motto (as Salus populi suprema lex, or Salus populi suprema est). and appears on the coat of arms, of the City of Salford, the London Borough of Lewisham, Eastleigh, Harrow, Lytham St. Anne's, Tipton, Mid Sussex, West Lancashire, Swinton and Pendlebury, Urmston and Willenhall; Manassas Park, Virginia, the Duquesne University School of Law, and is used as the motto of the Vlaams Belang political group in the Belgian Chamber of Representatives. The phrase is also used by the Ministry of Interior of the Slovak Republic as an element on it´s coat of arms.
John Locke uses it as the epigraph in his Second Treatise on Government and refers to it as a fundamental rule for government. It was the inscription on the coronet of Roundhead and Leveller William Rainsborowe during the English Civil War. This motto was also endorsed by Hobbes at the beginning of Chapter 30 of Leviathan and by Spinoza in Chapter 19 of his Theological-Political Treatise.
The motto was featured on the masthead of the Irish medical journal Medical Press and Circular.
It is the motto of the South Australia Police, which was established in 1838. The Commissioned Officers Association of the U.S. Public Health Service has adopted the phrase as its motto.
The Italian Army uses a similar motto, Salus Rei Publicae Suprema Lex Esto ("The safeguard of the republic shall be the supreme law").