Bose gas is a concept in quantum mechanics.

Classical mechanics has a concept called ideal gas. This concept describes how a gas usually behaves, in different settings. A bose gas is the analogous concept in quantum mechanics.

A bose gas is made of bosons with a positive spin value. These bosons also follow the Bose-Einstein statistics. The statistical mechanics of bosons were developed by Satyendra Nath Bose for photons. Albert Einstein extended the theory, when he realized that an ideal gas of bosons would form a condensate at a low enough temperature. This condensate is known as a Bose–Einstein condensate. This is not the case with a classical ideal gas.