Dugan or Duggan ( ) is an Irish surname that arose simultaneously in a number of areas, including Cork, Roscommon, Galway, Wexford and Fermanagh. The best known family of the name had its territory near the modern town of Fermoy in north Cork, and were originally the ruling family of the Fir Maighe tribal group which gave its name to the town. They claimed descent from Mug Ruith, the legendary magician of the Fir Bolg. They ceded pre-eminence to the O'Keeffe family in the eleventh century, but remained powerful in the area. Along with the other Fir Maighe families they lost their power when the Normans conquered the territory in the twelfth and thirteenth centuries.

The Coat of Arms are azure with a crescent argent between nine stars of eight points. The motto, Virtve et Valore ("By Virtue and Valor") is derived from Old English rather than from the Irish translation of Ó Dubhagáin, meaning "dark" or "black." The motto is derived from the Old English word dūgan (preterite-present: dēag ‘it is useful', dugon ‘they are useful', dohte ‘it was useful'). Other definitions include "to avail, to be of use, to serve"; Ðonne his ellea deah ("when his valour avails"); "to be fit or strong".

In modern day, the name is found throughout Ireland. In the north, Dugan, Dougan, and Doogan are common, a large portion descended from families originally in County Fermanagh. Doogan is common in County Donegal. Duggan is most prevalent in Dublin, Munster, and the majority of County Cork, County Tipperary, County Wexford, and County Waterford.

Dugan and Dougan are also common Scottish names. Throughout other English speaking countries, Dugan and its many variants, including Duggan, Dougan, Doughan, Doogan, and Duggin are widespread. Dugan ranked 1,705 in surname listings in the 1990 United States Census. In Great Britain, Duggan ranked 1,950 in surname listings from the 1881 Census, then surged to 1,025 in surname listings from the 1996 Electoral roll.

Notable people

• Benjamin Hayes Dougan, Canadian physician, politician
• Brady Dougan (born 1959), CEO of the investment banking group Credit Suisse
• Chris Dugan (born 1989) Bassist of Minneapolis-based pop punk band duncecapkids.
• Dennis Dugan (born 1946), American actor and film director
• Derek Dougan (1938 – 2007), professional footballer
• Eamonn Duggan (1874 – 1936), Irish nationalist signatory to the Anglo-Irish Treaty in 1921 and Minister of Home Affairs in the first Irish Free State government
• James Duggan (1825-1899), catholic bishop of Chicago
• Jeff Dugan (born 1981), American footballer player with the Minnesota Vikings
• Jeremiah Duggan (1980 – 2003), a British student at the Sorbonne, died in disputed circumstances near Wiesbaden, Germany.
• Jim Duggan (born 1954), American professional wrestler
• Joe Dugan (1897 - 1982), American baseball player from 1917-1931
• General Michael Dugan (born 1937), former Chief of Staff of the United States Air Force
• Noel Duggan, musician and member of Grammy-winning band Clannad
• Pádraig Duggan, musician and member of Grammy-winning band Clannad
• Raymond Smith Dugan, (1878-1940), American Astronomer, textbook author and professor at Princeton University
• Major General, Sir Winston Joseph Dugan (1877–1951), British administrator who served as governor of South Australia
• The Duggans, Irish musical duo from Gweedore, County Donegal