This paper examines the properties of the fictional metal vibranium, found in the Marvel Cinematic Universe, to ascertain whether it is scientifically plausible. It identifies that vibranium is a very strong, extremely hard, tough metallic material with a density of around 2,700 kg m⁻³ and is highly efficient at absorbing vibrational energy. It shows that vibranium cannot be an as yet undiscovered element. Similarly, it is argued that it cannot be based on a 2D material such as graphene. It is suggested that vibranium derives some of its strength from reinforcement with a ceramic, probably in the form of a fibre. Additionally, it shows that vibranium is an as yet undiscovered high entropy alloy which exhibits an appropriate combination of strength and toughness. The damping capability of vibranium is likely to arise from a shape memory effect in which mechanical energy is rapidly dissipated by a reversible martensitic phase transformation. Such a complex material lies outside the scope of modern materials science.