ELF may be:

Science

• Electron localization function, a concept in quantum mechanics
• Extremely low frequency, the band of radio frequencies from 3 to 30 Hertz

An elf (plural: elves) is a type of supernatural being in Germanic mythology and folklore. Elves are first attested in Old English and Old Norse texts and are prominent in traditional British and Scandinavian folklore.

In computing, the Executable and Linkable Format (ELF, formerly called Extensible Linking Format) is a common standard file format for executables, object code, shared libraries, and core dumps. First published in the  System V Application Binary Interface specification, and later in the Tool Interface Standard, it was quickly accepted among different vendors of Unix systems. In 1999 it was chosen as the standard binary file format for Unix and Unix-like systems on x86 by the 86open project.