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The Belt of Venus or Venus's Girdle or Twilight Wedge is an atmospheric phenomenon seen shortly before sunrise or shortly after sunset. The observer is, or is very nearly, surrounded by a pinkish glow (or anti-twilight arch) that extends roughly 10°–20° above the horizon.
Like alpenglow, backscattering of reddened sunlight also creates the Belt of Venus. Unlike the Belt of Venus, the direct illumination of clouds and aerosols that create the afterglow which characterizes alpenglow hover low in the atmosphere and create a red horizontal band visible just after sunset or before sunrise. Unlike alpenglow, the sunlight refracted in the fine dust particles that create the rosy pinkish arch of the Belt of Venus hover high in the atmosphere and perpetuate it long after sunset or long before sunrise. In a way, the Belt of Venus is a true alpenglow visible at twilight near the anti-solar point.
Often, the glow is separated from the horizon by a dark layer, the Earth's shadow or "dark segment." The arch's light pink color is due to backscattering of reddened light from the rising or setting Sun. A very similar effect can be seen during a total solar eclipse. The zodiacal light, which is caused by reflection of sunlight from the interplanetary dust in the solar system, is also a similar phenomenon.
The name of the phenomenon alludes to the cestus, a girdle or breast-band, of the Ancient Greek goddess Aphrodite, customarily equated with the Roman goddess Venus.