Richard Avenarius (1843 - 1896) was the formulator of the radical positivist doctrine of empirio-criticism .

He believed that scientific philosophy must be purely descriptive definitions of experience, which must be free of both metaphysics and materialism. His opposition to the materialist assertions of Karl Vogt resulted in a violent attack upon empirio-criticism by Lenin.

His principal works are Critique of Pure Experience (1888-90) and The Human Concept of the World (1891) which influenced Ernst Mach and, to a lesser extent, William James.