The Omega constant is the value of W(1) where W is Lambert's W function. The name is derived from the alternate name for Lambert's W function, viz., the Omega function.

The constant, Ω, is approximately 0.5671. It has properties that are akin to those of the golden ratio, in that

e ^{- Ω} = Ω

or equivalently,

ln(1 / Ω) = Ω.

One can calculate Ω iteratively, by starting with an initial guess Ω₀, and considering the sequence

This sequence will converge towards Ω as n→∞.