Tullow (/ˈtʊloʊ/; Irish: An Tulach, meaning 'the hillock', formerly Tulach Ó bhFéidhlim/ Tullowphelim) is a market town in County Carlow, Ireland. It is located on the River Slaney where the N81 road intersects with the R725. As of 2022, the population was 5,138.
 Anglo-Norman landowner Hugh de Lacy built a castle in Tullow c. 1181 at the site of a crossing on the river Slaney. The castle was captured by Oliver Cromwell in 1650. There are no extant remains of the castle and the circumstances of its demolition are uncertain. The castle may have been pulled down during the reign of Queen Anne and the stones used in the construction of a barracks in the town.
 A monastery and school was founded in the fifth-century in Tullow by St Fortchern (or Fortiarnán), a pupil of St Patrick and St Lommán. Although there are no traces of the monastery today, a  granite font and cross base at St. Columba's Church in Tullow may be associated with it. Tullowphelim holy well is located on Barrack Street in Tullow. It is dedicated to the Virgin Mary, mother of Jesus. It is reputed to be the site of the monastery founded by St Fortiarnán. The current shrine dates to the 1920s. A pattern was held annually on 8 September until about 1800.
 Tullow was also the site of an Augustinian friary. During the dissolution of the monasteries, the land belonging to the friary was granted to James Butler, 9th Earl of Ormond. Similarly to Tullow Castle, the friary buildings were demolished but the exact date is uncertain. The Abbey Cemetery is located within the site of the former monastery.
 There is a statue of Father John Murphy, one of the leaders of the 1798 Rebellion, who was captured near Tullow and executed in the Market Square on 2 July. There is a small museum with information about this period and other local history located in the former Tullow Methodist church on Bridge Street.
 Bishop Daniel Delany founded the Brigidine Sisters in Tullow in 1807.
 Saint Patrick's are the GAA club in Tullow who currently compete in the Carlow Junior A Football Championship and have been crowned champions on ten occasions. They also compete in the Carlow Intermediate Hurling Championship.
 Parkville United AFC, who play at Hawkins Lane Tullow, compete in the Carlow premier division and Slaney Rovers AFC from Rathvilly, who play at Tullow town pitch.
 Tullow RFC are the local rugby team. Former Ireland international player Seán O'Brien played with the club.
 Emerald Darts are a Darts Academy situated at Floor 1 Post Office Sorting Office (At The Back Of Supervalu) who are the ONLY Darts Academy in Ireland who compete against other Darts Academies worldwide in the Junior Darts Corporation (JDC) grading system affiliated to The Professional Darts Corporation (PDC) and various national tournaments, Kian Cullen represented Emerald Darts in the JDC European Championships in the UK in December 2016.
Emerald Darts are proudly sponsored by Unicorn Darts the biggest dart manufacturer in the world.
 There is quote in Brendan Behan's Borstal Boy that mentions Tullow: "Littlewood was twenty and married. We thought he was as old as the Hills of Tullow."
 The town was at one time connected to the Irish railway network, on a branch line from Naas in County Kildare. Tullow railway station opened on 1 June 1886, closed for passenger and goods traffic in 1947 and finally closed on 1 April 1959.
 Bus Éireann route 132 provides a once a day each way (Mondays to Fridays inclusive) commuter link to Dublin via Tallaght. There are also a limited range (usually one/two journeys a day each way) of Bus Éireann Expressway services linking the town to Dublin, New Ross, Waterford and Rosslare Europort. JJ Kavanagh and Sons route from Hacketstown to Carlow also serves the town. The main stopping place for buses is on the Square.
 A local weather station operates in Tullow, which records all local weather and provides a five-day local forecast. Tullow recorded the lowest temperature in 2010 at −17.7 °C. It is also based in a basin so the weather patterns are slightly different.
 Tullow Oil is one of Europe's largest independent exploration and production companies with worldwide operations.