The bay is about 10 kilometres wide along its north–south base, and 7 km in length to its apex at the centre of the city of Dublin; stretching from Howth Head in the north to Dalkey Point in the south.

North Bull Island is situated in the northwest part of the bay, where one of two major inshore sand banks lay, and features a 5 km long sandy beach, Dollymount Strand, fronting an internationally recognised wildfowl reserve.

The metropolitan area of the city of Dublin surrounds three sides of the bay (the north, west, and south), while the Irish Sea lies to the east.

Other flows into the bay include two streams in Sutton, one at Kilbarrack, four crossing Raheny, and one each in Clontarf, Sandymount, Merrion, Booterstown and Blackrock, as well as two in greater Dún Laoghaire.

[2][3] One dominating feature of the skyline round the bay are the 207 metres (679 ft) chimney stacks of the Poolbeg Generating Station which have become a protected structure since 2014.

Ptolemy's map of Ireland (AD 140)places a settlement called "Eblana" and a river Oboka in the region of Dublin Bay.

The plan was vigorously opposed by environmentalists, including Dublin City Councillor Seán D. Loftus, on the grounds that it posed a serious risk of pollution.

Other suggestions for the bay have included a proposal to build giant underwater gas storage tanks, and to infill the near-lagoon behind North Bull Island to form a leisure park.

An Bord Pleanála rejected nine out of ten of its own inspector's recommendations for refusal, but refused permission on the basis that it was not satisfied that the proposed development would not adversely affect the integrity of the South Dublin Bay and River Tolka Estuary proposed Special Protection Area and adversely affect the natural heritage of Dublin Bay.

The bay has been subject to pollution from the inflowing watercourses, shipping and port activity, the main water treatment plant for Dublin and sewage discharges at other points, and at times some of its bathing areas are unavailable.

James Joyce set much of the action in his novel Ulysses around the bay, from the Forty Foot bathing place—in which the character Buck Mulligan washed on Bloomsday morning—to Howth, where Leopold Bloom made love to his wife Molly under the rhododendrons.