A composite railway sleeper (1; 50; 100) comprising an outer coating shell (2; 51; 101) made of composite plastic material and a shaped structural core (3; 52; 102), made of a material comprising at least concrete contained within said outer coating shell (2; 51; 510; 101), wherein said outer coating shell (2; 51; 510; 101) presents in the upper outer face (2a; 51a; 101a) two distinct and opposite groups of grooves (4; 53) suitable to receive the angular guide plates (G) belonging to pre-assembled elastic type fastening systems (64) for the connection of two respective rails (R) with said railway sleeper (1; 50; 100).