UDF may refer to:
Astronomy Ultra Deep Field, a view of the distant universe taken in 2004 by the Hubble space telescope UDF 423, a distant spiral galaxy UDF 2457, a red dwarf star
Computing Universal Disk Format, an operating-system-independent file system commonly used on DVD and other digital media Uniqueness Database File, a Windows XP Professional configuration text file User-defined function, a function provided by the user of a program or environment
Organizations Politics United Democratic Forces (ОДС), an electoral alliance in Bulgaria United Democratic Forces of Belarus, a coalition of political parties participating as the main opposition group during the 2006 presidential election United Democratic Front (Botswana) United Democratic Front (Kerala), India United Democratic Front (Mizoram), India United Democratic Front (Malawi) United Democratic Front (Namibia) United Democratic Front (Pakistan) United Democratic Front (South Africa) United Democratic Front (South Sudan) United Democratic Forum Party, a former political party in Kenya Union pour la Démocratie Française (Union for French Democracy), a former centrist pro-European French political party
Military Ulster Defence Force, a paramilitary group in Northern Ireland Union Defence Force (South Africa), the predecessor of the South African Defence Force from 1912 to 1957 Union Defence Force (UAE), the armed forces of the United Arab Emirates
Other organizations United Dairy Farmers, an American chain of ice cream shops
Other uses Unducted fan, another name for a propfan engine United Defense Force, a fictional global military in the manga All You Need Is Kill and its film adaptation Edge of Tomorrow
See also Union of Democratic Forces (disambiguation), several political parties