Silybum marianum (milk thistle) is currently utilised as a medicinal plant which provides raw material for the production of silymarin. Silymarin is composed of a group of flavonolignans that are well known and studied for their medicinal properties. However, the biomass yield potential and the chemical composition of its biomass suggest opportunities for much broader utilisation of S. marianum. This paper reviews the available literature about S. marianum biomass productivity and composition and about properties of products and byproducts of silymarin extraction. Alternative uses of whole plant biomass include fodder, bioenergy production and phytoremediation. Byproducts of silymarin extraction such as oil and flour have possible applications in food, feed and cosmetics. Moreover, the review explores potential alternative applications of silymarin. We conclude that a pivotal issue for further utilisation of S. marianum is the development of improved cultivars suited for the different possible utilisations.