The district was originally a village just outside Dublin, surrounded by landed estates.
In the early years of the Irish Confederate Wars (1641–1649) the area was the scene of skirmishes culminating in the Battle of Rathmines in August 1649. After the Irish united with the Royalists against the Parliamentarians, an attempt was made to take Dublin. Their army under Ormonde was defeated, many of them killed, and the place where they fell (mainly between Rathmines and Ranelagh) was known for a long time as the Bloody Fields.
In 1785, only two years after the first manned flight, Richard Crosbie successfully flew in a hot air balloon from Ranelagh Gardens to Clontarf. The 225th anniversary of his flight was commemorated with a balloon flight from the same gardens on 23 January 2010 although due to adverse weather the balloon did not take off.
The area was incorporated into the expanding city in the 19th century, after which massive development took place.
The name Ranelagh applies to many geographical features. The stretch of road joining Sandford Road (which begins at the corner of Anna Villa) to Ranelagh Road (which begins at the railway bridge) is known as Ranelagh or Ranelagh Village. The whole surrounding area is also popularly known as Ranelagh, stretching from Charlemont Bridge on the Grand Canal at the northern end of Ranelagh Road down to the junction with Milltown Road at the southern end of Sandford Road, and from Leeson Street to the East towards Rathmines to the West. At the centre of Ranelagh is "Ranelagh Triangle", semi-officially "the Angle", which is the junction of Ranelagh Village and Charleston Road. Nearby restaurant "Tribeca" references these geographical features (i.e., Tri-angle Be-low Ca-nal). To the North of the Triangle is the "Hill Area" of Ranelagh, which was the scene of Lee Dunne's novel, "Goodbye to the Hill". Ranelagh contains many fine Victorian streets such as those surrounding Mount Pleasant Square.
The townlands of Ranelagh North and Ranelagh South are in the civil parish of St. Peter's and in the barony of Uppercross. They are bounded on the north by Harcourt Road and Adelaide Road, on the east by Sussex Road and an old irregular boundary from there to Chelmsford Road, on the south by Chelmsford Road, Ranelagh Village, Charleston Road, Oakley Road and Dunville Avenue, and on the west by Beechwood Park, Belgrave Square East, Mountpleasant Avenue Upper, Bessborough Parade, Rathmines Road Lower and Richmond Street South. The area popularly known today as Ranelagh also includes parts of the adjoining townlands of Cullenswood, Sallymount and Milltown. 
Ranelagh is in the local government electoral area of Pembroke/Rathmines, which is to be reconfigured as Rathgar-Rathmines Local Electoral Area with effect from May 2014. It is located in the Dáil Constituency of Dublin South-East, which is renamed Dublin Bay South with effect from the 2016 General Election.
There are several primary and secondary schools in the area.
Lios na nÓg, another gaelscoil, is located in Cullenswood House on Oakley Road, where St. Enda's School (Scoil Éanna) was set up by Patrick Pearse in 1908. This was the first school in Ireland where pupils were taught in both Irish and English. St. Enda's school then moved to Rathfarnham in 1912 leaving the school building, Cullenswood House, unoccupied. In 1998, Lios na nÓg moved in and the school went under a major refurbishment over the period 2008-'09.
The Ranelagh Multi-Denominational School, is another primary school established in September 1988, which is located on the main Ranelagh road close to the luas stop. It is on the site of the old St.Columba's national school, which was donated to RMDSA by the Church of Ireland. The school won many awards for the great architecture of the building, built late 1990s. Other primary schools in the area include Sandford National, located close to Gonzaga College.
- The green Luas line passes through, and stops at, Ranelagh/Raghnallach (on Ranelagh Road) and also at Beechwood, built on the site of the former Ranelagh Railway Station on the Harcourt Street railway line (the station opened as Ranelagh & Rathmines on 16 July 1896, was renamed Ranelagh in 1921 and finally closed on 1 January 1959.
- The 11, 18, 44, and 61 bus routes pass through Ranelagh.
- The area is, and was, the home of some of Ireland's leading politicians:
- Garret FitzGerald, who was Taoiseach (Prime Minister) of Ireland twice in the 1980s, lived the last years of his life at Anna Villa in Ranelagh
- Former Tánaiste and Minister for Justice Michael McDowell lives in Ranelagh off the triangle
- Former President of Ireland and UN High Commissioner Mary Robinson was a resident of the area
- Robert Briscoe, former Lord Mayor of Dublin and TD was born on Lower Beechwood Avenue, Ranelagh
- Former Fianna Fáil TD, Michael Mulcahy, lives in the Beechwood area of Ranelagh
- Politician Eamon Ryan lived in the Ashfield Road area for a time
- Ranelagh is the birthplace and childhood home of Hollywood actress Maureen O'Hara
- Wilfrid Brambell, film and television actor best known for his role in the British television series Steptoe and Son was raised on Edenvale Road
- Maeve Brennan, short story writer and long-time journalist with The New Yorker magazine, was born and raised in Ranelagh; she set the majority of her fiction in a terraced house here
- Former World snooker champion Ken Doherty is from the area and used to practice in local snooker club, Jason's (demolished in 2012)
- Nell McCafferty, Northern Irish civil rights campaigner and journalist, has lived in Ranelagh for several years
- Actor Eamon Morrissey grew up in Ranelagh
- John Mulholland, editor of the UK newspaper The Observer
- Brendan O'Reilly, Olympian, RTÉ commentatator,journalist, singer, songwriter, actor, author, lived in Ranelagh for many years until his death in 2001
- Eamon Dunphy, Irish media personality, broadcaster, author, sports pundit and former professional footballer, lives in Ranelagh.
- Founded in 2003, Ranelagh Gaels first commenced competitive action in 2004. They recently topped the league in Division 9 and now competed in League 8, and grade C in the Dublin county championship. They play their home games in Bushy Park in Terenure, and train in UCD.
- They have recently started a ladies team, which will compete in the league in 2010. The Ladies won the Dublin Junior E Championship in 2010. The first Championship the club has ever won.
- F. Elrington Ball: A History of the County Dublin. 1903. Part II. page 103 et passim
- Rice, Eoghan (2006-12-17). "First Irishman to take to the skies to be honoured". Archived from the original on 2007-11-22. Retrieved 2007-04-09.
- Ranelagh Arts Festival
- Scoil Bhríde
- "Rathmines and Ranelagh station" (PDF). Railscot - Irish Railways. Retrieved 2007-11-23.
- Well Whooley God! (Sep 9, 2010) Ranelagh Gaels 2-9 Scoil Ui Chonaill 2-7
- Ranelagh Gaels GAA Football Club
- InRanelagh.com - local site for Ranelagh
- Ranelagh Arts Festival
- RateMyArea.com - local information resource for Ranelagh Area
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