An object of the present invention is to provide a multicomponent copolymer for use for producing a crosslinked rubber composition and a rubber product excellent in fracture performance (strength and elongation) at high temperatures while maintaining high weather resistance. Further, the invention provides a rubber composition containing the multicomponent copolymer, a crosslinked rubber composition obtained by crosslinking the rubber composition, and a rubber product and a tire using the rubber composition or the crosslinked rubber composition. The multicomponent copolymer of the invention contains a conjugated diene unit, a non-conjugated olefin unit and an aromatic vinyl unit, wherein the main chain is formed of an acyclic structure alone, the content of the aromatic vinyl unit is 3 mol % or more of the whole multicomponent copolymer, and the content of the non-conjugated olefin unit is more than 44 mol % and less than 97 mol % of the whole multicomponent copolymer.