thumb|300px|A truncated biconical antenna showing the typical [[pernach|"mace head" shape]]
In radio systems, a biconical antenna is a broad-bandwidth antenna made of two roughly conical conductive objects, nearly touching at their points.
Biconical antennas are broadband dipole antennas, typically exhibiting a bandwidth of three octaves or more. A common subtype is the bowtie antenna, essentially a flattened version of the biconical design which is often used for short-range UHF television reception. These are also sometimes referred to as butterfly antennas.
Sir Oliver Lodge is the inventor of the biconical antenna.
175px|right|thumb|Omnidirectional biconical antenna
Properties
The biconical antenna has a broad bandwidth because it is an example of a traveling wave structure; the analysis for a theoretical infinite antenna resembles that of a transmission line. For an infinite antenna, the characteristic impedance at the point of connection is a function of the cone angle only and is independent of the frequency.
Practical antennas have finite length and a definite resonant frequency.