OEF

OEF may refer to:
 * Obscene Extreme Festival, an annual music festival in the Czech Republic since 1999
 * Operation Enduring Freedom, official U.S. government name for "the Global War on Terrorism" 2001–2014
 * Order of Ecumenical Franciscans, a religious sub-order of the Franciscans
 * Oxygen Extraction Fraction, a measure of oxygen utilization efficiency