In principle, a sheriff is a legal official with responsibility for a county. In practice, the specific combination of legal, political, and ceremonial duties of a sheriff varies greatly from country to country.

The word "sheriff" is a contraction of the term "shire reeve". The term, from the Old English scīrgerefa, designated a royal official responsible for keeping the peace (a "reeve") throughout a shire or county on behalf of the king. The term was preserved in England notwithstanding the Norman Conquest. From the Anglo-Saxon kingdoms the term spread to several other regions, at an early point to Scotland, latterly to Ireland, and to the United States.

Sheriffs exist in various countries:

In British English, the political or legal office of a sheriff is called a shrievalty.

The office of sheriff was first established in Australia in 1824. This was simultaneous with the appointment of the first Chief Justice of New South Wales. The role of the sheriff has not been static, nor is it identical in each Australian State. In the past his duties included: executing court judgements, acting as a coroner, transporting prisoners, managing the gaols, and carrying out executions (through an anonymous hangman). Currently, no Australian State provides for capital punishment. A government department (usually called the Department of Corrections or similar) now runs the prison system, and the Coroner’s Office handles coronal matters. The sheriff is now largely responsible for enforcing the civil orders and fines of the court (seizing and selling the property of judgement debtors who do not satisfy the debt), providing court security, enforcing arrest warrants, evictions, taking juveniles into custody, and running the jury system. Some State Sheriffs can also apply sanctions ranging from suspending drivers licences and car registration to wheel clamping and arranging community service orders, and as a last resort make arrests.