An officer of arms is a person appointed by a sovereign or state with authority to perform one or more of the following functions:
The medieval practice of appointing heralds or pursuivants to the establishment of a noble household is still common in European countries, particularly those in which there is no official heraldic control or authority. Such appointments are also still made in Scotland, where four private officers of arms exist. These appointments are all purely advisory.
Work completed by the Canadian Heraldic Authority is conducted by officers known as the herald of arms. The organization is led by the Herald Chancellor of Canada and the Chief Herald of Canada, the latter serving as the director for the heraldic authority.  In addition to the Chief Herald, other herald of arms includes the Athabaska Herald, Assiniboine Herald, Coppermine Herald, Fraser Herald, Miramichi Herald, Saguenay Herald, and the Saint-Laurent Herald. 
In addition to the herald in ordinary, several retired heralds and notable individuals were named to the honorary position of Herald Emeritus or Heralds Extraordinary. This includes the Albion Herald Extraordinary, Capilano Herald Extraordinary, Cowichan Herald Extraordinary, Dauphin Herald Extraordinary, Niagara Herald Extraordinary, Rouge Herald Extraordinary, Outaouais Herald Emeritus, and the Rideau Herald Emeritus. 
In the Republic of Ireland, matters armorial and genealogical come within the authority of an officer designated the Chief Herald of Ireland. The legal basis for Ireland's heraldic authority, and therefore all grants since 1943, has been questioned by the Attorney General,  therefore, on 8 May 2006, Senator Brendan Ryan introduced the Genealogy & Heraldry Bill, 2006,  in Seanad Éireann (Irish Senate) to remedy this situation and legitimise actions since the transfer of power from the Ulster King of Arms.
In the Netherlands, officers of arms do not exist as permanent functions. Private heraldry is not legislated, and state heraldry and the heraldry of the nobility is regulated by the private High Council of Nobility.
However, two kings of arms and two or four heralds of arms have figured during royal inauguration ceremonies. These were usually members of the High Council of Nobility. During the inaugurations of Wilhelmina and Juliana, the kings of arms wore nineteenth-century-style court dress, whereas the heralds wore tabards. All officers carried rods and wore chains of office.  In the inauguration of Queen Beatrix in 1980, members of the resistance posed as the ceremonial officers of arms, with Erik Hazelhoff Roelfzema being the elder king of arms.  Like most other participants in the pageant, the officers of arms were no longer wearing ceremonial dress, but white tie instead. The senior king of arms proclaims the king or queen to be inaugurated after he or she has sworn allegiance to the constitution. The heralds step outside the New Church in Amsterdam, where the inauguration ceremony is held, to announce this fact to the people gathered outside the church. 
In England, the authority of the thirteen officers of arms in ordinary, who form the corporation of the kings, heralds and pursuivants of arms (College of Arms), extends throughout the Commonwealth, with the exception of Scotland, Canada and South Africa.
Officers of arms are of three ranks: kings of arms, heralds of arms, and pursuivants of arms. Officers of arms whose appointments are of a permanent nature are known as officers of arms in ordinary; those whose appointments are of a temporary or occasional nature are known as officers of arms extraordinary. The officers of arms in ordinary who form the College of Arms are members of the royal household and receive a nominal salary.
In Scotland, the Lord Lyon King of Arms and the Lyon Clerk and Keeper of the Records control armorial matters within a strict legal framework not enjoyed by their fellow officers of arms in London, and the court which is a part of Scotland's criminal jurisdiction has its own prosecutor, the court's Procurator Fiscal, who is, however, not an officer of arms. Lord Lyon and the Lyon Clerk are appointed by the crown, and, with the Crown's authority, Lyon appoints the other Scottish officers. The officers of arms in Scotland are also members of the royal household.
A coat of arms is a heraldic visual design on an escutcheon, surcoat, or tabard. The coat of arms on an escutcheon forms the central element of the full heraldic achievement, which in its whole consists of a shield, supporters, a crest, and a motto. A coat of arms is traditionally unique to an individual person, family, state, organization, school or corporation. The term itself of 'coat of arms' describing in modern times just the heraldic design, originates from the description of the entire medieval chainmail 'surcoat' garment used in combat or preparation for the latter.
The Right Honourable the Lord Lyon King of Arms, the head of Lyon Court, is the most junior of the Great Officers of State in Scotland and is the Scottish official with responsibility for regulating heraldry in that country, issuing new grants of arms, and serving as the judge of the Court of the Lord Lyon, the oldest heraldic court in the world that is still in daily operation.
The College of Arms, or Heralds' College, is a royal corporation consisting of professional officers of arms, with jurisdiction over England, Wales, Northern Ireland and some Commonwealth realms. The heralds are appointed by the British Sovereign and are delegated authority to act on behalf of the Crown in all matters of heraldry, the granting of new coats of arms, genealogical research and the recording of pedigrees. The College is also the official body responsible for matters relating to the flying of flags on land, and it maintains the official registers of flags and other national symbols. Though a part of the Royal Household of the United Kingdom, the College is self-financed, unsupported by any public funds.
A pursuivant or, more correctly, pursuivant of arms, is a junior officer of arms. Most pursuivants are attached to official heraldic authorities, such as the College of Arms in London or the Court of the Lord Lyon in Edinburgh. In the mediaeval era, many great nobles employed their own officers of arms. Today, there still exist some private pursuivants that are not employed by a government authority. In Scotland, for example, several pursuivants of arms have been appointed by Clan Chiefs. These pursuivants of arms look after matters of heraldic and genealogical importance for clan members.
King of Arms is the senior rank of an officer of arms. In many heraldic traditions, only a king of arms has the authority to grant armorial bearings and sometimes certify genealogies and noble titles. In other traditions, the power has been delegated to other officers of similar rank.
The Canadian Heraldic Authority is part of the Canadian honours system under the Canadian monarch, whose authority is exercised by the Governor General of Canada. The authority is responsible for the creation and granting of new coats of arms, flags, and badges for Canadian citizens, government agencies, municipal, civic and other corporate bodies. The authority also registers existing armorial bearings granted by other recognized heraldic authorities, approves military badges, flags, and other insignia of the Canadian Forces, and provides information on heraldic practices. It is well known for its innovative designs, many incorporating First Nations symbolism.
New Zealand Herald of Arms Extraordinary is the officer of arms responsible for the regulation of heraldry in New Zealand. Although affiliated with the College of Arms in London, the New Zealand Herald lives and works in New Zealand, and is not a member of the College Chapter. The current New Zealand Herald of Arms Extraordinary is Phillip Patrick O’Shea.
Sir Malcolm Rognvald Innes of Edingight was Lord Lyon King of Arms of Scotland from 1981 until 2001.
The law of heraldic arms governs the "bearing of arms", that is, the possession, use or display of arms, also called coats of arms, coat armour or armorial bearings. Although it is believed that the original function of coats of arms was to enable knights to identify each other on the battlefield, they soon acquired wider, more decorative uses. They are still widely used today by countries, public and private institutions and by individuals. The earliest writer on the law of arms was Bartolus de Saxoferrato. The officials who administer these matters are called pursuivants, heralds, or kings of arms. The law of arms is part of the law in countries which regulate heraldry, although not part of common law in England and in countries whose laws derive from English law.
A herald, or a herald of arms, is an officer of arms, ranking between pursuivant and king of arms. The title is commonly applied more broadly to all officers of arms.
A private officer of arms is one of the heralds and pursuivants appointed by great noble houses to handle all heraldic and genealogical questions.
Finlaggan Pursuivant of Arms is the private officer of arms of the Clan Donald in Scotland.
Heraldry in Scotland, while broadly similar to that practised in England and elsewhere in western Europe, has its own distinctive features. Its heraldic executive is separate from that of the rest of the United Kingdom.
Elizabeth Ann Roads, is a former Scottish herald, an office from which she retired in 2021; in July 2018 she retired as Lyon Clerk at the Court of the Lord Lyon
The Cambridge University Heraldic and Genealogical Society was formed as the result of the merger in 1957 of a previous Heraldic Society with the Cambridge University Society of Genealogists.
Linlithgow Pursuivant of Arms is a Scottish pursuivant of arms of the Court of the Lord Lyon.
James Terry was an Irish officer of arms who remained faithful to the Jacobite kings of Britain after their escape to the European continent.
A heraldic authority is defined as an office or institution which has been established by a reigning monarch or a government to deal with heraldry in the country concerned. It does not include private societies or enterprises which design and/or register coats of arms. Over the centuries, many countries have established heraldic authorities, and several still flourish today.
The Court of the Lord Lyon is a standing court of law, based in New Register House in Edinburgh, which regulates heraldry in Scotland. The Lyon Court maintains the register of grants of arms, known as the Public Register of All Arms and Bearings in Scotland, as well as records of genealogies.
TheArmorial Register is a publisher of heraldic and associated science topics, founded in 2006. It produces the "International Register of Arms", a private armorial where people from all over the world can register their granted, inherited or assumed arms. However it has no jurisdiction over heraldic or genealogical matters. Its coat of arms is displayed on the website. From time to time, its "Roll of Arms" is edited into book format, of which there have been three volumes so far.