The flag of Leinster consists of an Irish harp

Clàrsach

Clàrsach or Cláirseach , is the generic Gaelic word for 'a harp', as derived from Middle Irish...

 in gold on a green background: vert

Vert

The colour green is commonly found in modern flags and coat of arms, and to a lesser extent also in the classical heraldry of the Late Middle Ages and the Early Modern period....

 a harp or

Or (heraldry)

In heraldry, Or is the tincture of gold and, together with argent , belongs to the class of light tinctures called "metals". In engravings and line drawings, it may be represented using a field of evenly spaced dots...

 stringed argent

Argent

In heraldry, argent is the tincture of silver, and belongs to the class of light tinctures, called "metals". It is very frequently depicted as white and usually considered interchangeable with it...

. The arms of Leinster

Leinster

Leinster is one of the Provinces of Ireland situated in the east of Ireland. It comprises the ancient Kingdoms of Mide, Osraige and Leinster. Following the Norman invasion of Ireland, the historic fifths of Leinster and Mide gradually merged, mainly due to the impact of the Pale, which straddled...

 are (among other examples) represented on the flag of the provinces of Ireland

Provinces of Ireland

Ireland has historically been divided into four provinces: Leinster, Ulster, Munster and Connacht. The Irish word for this territorial division, cúige, literally meaning "fifth part", indicates that there were once five; the fifth province, Meath, was incorporated into Leinster, with parts going to...

, as well as in a stylised version in the logo of the Leinster Rugby

Leinster Rugby

Leinster Rugby, usually referred to simply as Leinster, is an Irish professional rugby union team based in Dublin, representing the Irish province of Leinster, that competes in the RaboDirect Pro 12 and also competes in the Heineken Cup...

 team. The flag is sometimes used as a symbol of Irish nationalism

Irish nationalism

Irish nationalism manifests itself in political and social movements and in sentiment inspired by a love for Irish culture, language and history, and as a sense of pride in Ireland and in the Irish people...

 and to represent the island of Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

 as a whole.

Origins

Possibly the oldest instance of the use of the harp device on a green field was the flag of Owen Roe O'Neill

Owen Roe O'Neill

Eoghan Ruadh Ó Néill , anglicised as Owen Roe O'Neill , was a seventeenth century soldier and one of the most famous of the O'Neill dynasty of Ulster.- In Spanish service :...

. Owen Roe, nephew of Hugh, had entered the Spanish

Spain

Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

 service after his uncle's defeat at Kinsale

Siege of Kinsale

The Siege or Battle of Kinsale was the ultimate battle in England's conquest of Gaelic Ireland. It took place during the reign of Queen Elizabeth I, at the climax of the Nine Years War - a campaign by Aodh Mór Ó Néill, Aodh Rua Ó Dónaill and other Irish clan leaders against English rule...

 in 1601. Owen rose to prominence in the Spanish army, and in 1642 returned to Ireland to assist the Irish Confederation

Confederate Ireland

Confederate Ireland refers to the period of Irish self-government between the Rebellion of 1641 and the Cromwellian conquest of Ireland in 1649. During this time, two-thirds of Ireland was governed by the Irish Catholic Confederation, also known as the "Confederation of Kilkenny"...

 in the war that broke out the previous year. It is recorded that his ship, the St Francis, as she lay at anchor at Dunkirk, flew from her mast top "the Irish harp in a green field, in a flag". Because the confederation's headquarters were located in Kilkenny

Kilkenny

Kilkenny is a city and is the county town of the eponymous County Kilkenny in Ireland. It is situated on both banks of the River Nore in the province of Leinster, in the south-east of Ireland...

 – the principal city of Leinster "without the pale

The Pale

The Pale or the English Pale , was the part of Ireland that was directly under the control of the English government in the late Middle Ages. It had reduced by the late 15th century to an area along the east coast stretching from Dalkey, south of Dublin, to the garrison town of Dundalk...

" – his flag may have had a special significance for that province. The Confederation seal also incorporated, among a number of other motifs, a representation of the Irish harp.