Tullamore Dew is a brand of Irish whiskey produced by William Grant & Sons. It is the second largest selling brand of Irish whiskey globally, with sales of over 950,000 cases per annum as of 2015.

The whiskey was originally produced in the Tullamore, County Offaly, Ireland, at the old Tullamore Distillery which was established in 1829. Its name being derived from the initials of Daniel E. Williams (D.E.W.), a general manager and later owner of the original distillery. In 1954, the original distillery closed down, and with stocks of whiskey running low, the brand was sold to John Powers & Son, another Irish distiller in the 1960s, with production transferred to the Midleton Distillery, County Cork in the 1970s following a merger of three major Irish distillers.

In 2010, the brand was purchased by William Grant & Sons, who constructed a new distillery on the outskirts of Tullamore. The new distillery opened in 2014, bringing production of the whiskey back to the town after a break of sixty years.

In 2012, a visitor centre was opened in a refurbished bonded warehouse previously belonging to the original distillery. The centre offers guided tours and tutored tastings ranging from 50 minutes to 5 hours in duration.

The origins of Tullamore Dew date back to 1829, when a distillery was established in Tullamore by Michael Molloy. On his death, the distillery eventually passed to his nephew, Bernard Daly who later appointed Daniel E. Williams as the distillery's General Manager. Under Williams's watchful eye, the distillery expanded and prospered, launching the whiskey bearing his initials (D.E.W.), Tullamore Dew.

In 1954, the distillery ceased production, having, like many of those in Ireland at the time, been hit by declining sales due to a number of factors such as Prohibition, the Anglo-Irish Trade War and high taxes introduced by the Irish Free State.

In the 1960s, with whiskey stocks running low, rather than reopen the distillery, the owners opted to sell the brand to John Powers & Son, the Dublin distillers. In 1966, John Powers & Son merged with two other Irish distilleries to form Irish Distillers. In the 1970s, Irish distillers closed their existing distilleries and consolidated production at a new distillery built in Midleton, County Cork.

In 1994, Irish Distillers, then concentrating their international focus on promoting Jameson Irish whiskey, sold the brand to the C&C Group. Subsequently, the C&C Group divested their entire liqueur and spirit business (including Tullamore Dew), which was acquired by William Grant & Sons for €300 million in 2010. At which point, Tullamore Dew was still being produced under license by at the Midleton Distillery. Therefore, as expansion of the brand was dependent on the availability of whiskey from Midleton, and with significant growth envisaged, William Grant & Sons opted to construct a new distillery in Tullamore, rather than depend on outsourced production.

Construction of the distillery is to take place on a phased basis. Phase one was completed in 2014, which saw production of whiskey return to Tullamore for the first time in sixty years. The new distillery has the capapability to produce both malt and pot still whiskey. However, it does not yet have a Coffey still installed to allow the production of grain whiskey. Therefore, as Tullamore Dew is a blend of all three varieties of Irish whiskey, the grain whiskey component of the blend will continue to be sourced from Midleton until phase two is completed.

As of 2015, the whiskey sells about 950,000 cases per year (an amount that has doubled since 2005).