Avidya - Ignorance of the Self
The fundamental ignorance that creates bondage.
Avidya is not mere lack of information but the positive misapprehension of the Self as limited. It mistakes the not-self for Self and is the root of all suffering.
Through ignorance we take the transient for the eternal, the impure for the pure, pain for pleasure, and the not-self for the Self.
Avidya is beginningless but ends with knowledge.
Various Upanishads