Light Blue may refer to:

• Light blue, a variant of the color blue
  • Light blue
  • Light blue (RAL), a RAL color
• "Light Blue", a song by Thelonious Monk on the 1958 jazz album Thelonious in Action
• "Light Blue", a song by Snail Mail on the 2021 indie rock album Valentine
• Light Blue Pour Homme, a men's fragrance
• Light Blue Sun, an album by Lili Haydn
• Light Blue: Arthur Blythe Plays Thelonious Monk, an album by Arthur Blythe
• MRT Light Blue Line, a planned mass rapid transit line to be built in Bangkok, Thailand

Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz. The visible band sits adjacent to the infrared and the ultraviolet, called collectively optical radiation.

Blue is one of the three primary colours in the RGB (additive) colour model, as well as in the RYB colour model. It lies between violet and cyan on the spectrum of visible light. The term blue generally describes colours perceived by humans observing light with a dominant wavelength that's between approximately 450 and 495 nanometres. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called the Tyndall effect explains blue eyes. Distant objects appear more blue because of another optical effect called aerial perspective.