Howth is located on the peninsula of Howth Head, which begins around 13 kilometres (8.1 mi) east-north-east of Dublin, on the north side of Dublin Bay. The village itself is located 15 kilometres (9.3 mi) from Dublin city centre (the ninth of a series of eighteenth century milestones from the Dublin General Post Office (GPO) is in the village itself), and spans most of the northern part of Howth Head, which was once an island but now is connected to the rest of Dublin via a narrow strip of land (tombolo) at Sutton. Howth is located in the administrative county of Fingal.

Howth is at the end of a regional road (R105) from Dublin and is one of the two northern termini of the DART suburban rail system. Dublin Bus also serves Howth with route 31 and its variants the 31a and 31b. Previously the 88 bus operated around Howth Head operating as a replacement for the Hill of Howth Tramway.

Howth, in addition to its fishery harbour, hosts a substantial marina, and a seasonal boat service to the uninhabited island of Ireland's Eye.

The Irish name for Howth is Binn Éadair, meaning Éadair's Peak or Hill. In Old Irish, the name is recorded as Etar, which was first plundered by the Vikings around 819. The name Howth is thought to be of Norse origin, perhaps being derived from the Old Norse Hǫfuð ("head" in English). Norse vikings colonised the eastern shores of Ireland and built the settlement of Dyflinn (one of two settlements which became Dublin) as a strategic base between Scandinavia and the Mediterranean.

In ancient history Ptolyemy's second century map of Ireland shows Howth as an island named Edri Deserta (sometimes rendered as Edros).

After Brian Ború, the High King of Ireland, defeated the Norse in 1014, many Norse fled to Howth to regroup and remained a force until their final defeat in Fingal in the middle of the 11th century. Howth still remained under the control of Irish and localised Norse forces until the invasion of Ireland by the Anglo-Normans in 1169.
Without the support of either the Irish or Scandinavian powers, Howth was isolated and fell to the Normans in 1177. One of the victorious Normans, Armoricus (or Almeric) Tristram, was granted much of the land between the village and Sutton. According to the historian Samuel Lewis:
In 1177, Sir Amorey Tristram and Sir John de Courcy landed here at the head of a large military force, and totally defeated the Danish inhabitants in a sanguinary battle at the bridge of Evora, over a mountain stream which falls into the sea near the Baily lighthouse. This victory secured to Sir Amorey the lordship of Howth, of which his descendants have continued in possession to the present day, under the name of St. Laurence, which Almaric, third baron, assumed in fulfilment of a vow previously to his victory over the Danes near Clontarf, in a battle fought on the festival of that saint. The territory of Howth was confirmed to Almaric de St. Laurence by King John....

Tristam built his first castle overlooking the harbour and the St. Lawrence link remained until 2019 (see Earl of Howth). The original title of Baron of Howth was granted to Almeric St. Lawrence by Henry II of England in 1181, for one Knight's fee.

Howth was a minor trading port from at least the 14th century, with both health and duty collection officials supervising from Dublin, although the harbour was not built until the early 19th century.

A popular tale concerns the clan leader and sometime pirate Gráinne O'Malley, who was rebuffed in 1576 while attempting a courtesy visit to Howth Castle, home of the Earl of Howth. In retaliation, she abducted the Earl's grandson and heir, and as ransom she exacted a promise that unanticipated guests would never be turned away again. She also made the Earl promise that the gates of Deer Park (the Earl's demesne) would never be closed to the public again, and the gates are still open to this day, and an extra place is set for unexpected guests during formal dinners in the dining room.

In the early 19th century, Howth was chosen as the location for the harbour for the mail packet (postal service) ship. One of the arguments used against Howth by the advocates of Dún Laoghaire was that coaches might be raided in the badlands of Sutton (at the time Sutton was open countryside).[1] However, due to silting, the harbour needed frequent dredging to accommodate the packet and eventually the service was relocated to Dún Laoghaire. George IV visited the harbour in August 1821.

On the 26 July 1914, 900 rifles were landed at Howth by Erskine Childers for the Irish Volunteers. Many were used against the British in the Easter Rising and in the subsequent Anglo-Irish War. Among the members of the Howth branches of the Irish Volunteers and Cumann na mBan who participated in this event were the well-known writers Padraic Colum and Mary Colum. Members of both the Howth Volunteers and Baldoyle section of the Irish Citizen Army participated in the Easter Rising in Dublin city and in Fingal. A strong local branch of Sinn Féin developed in the area and there was considerable local involvement in both the Irish War of Independence and Irish Civil War. The harbour was radically rebuilt by the Office of Public Works in the late 20th century, with distinct fishing and leisure areas formed, and the installation of a modern ice-making facility. A new lifeboat house was later constructed, and Howth is today home to units of both the RNLI (lifeboat service) and the Irish Coastguard. In 2019, Howth Castle and its demesne, including Ireland’s Eye, were sold to Tetrarch Investment group, with an element of the site close to the demesne gate immediately sold on again for development, to Glenveagh Properties.