Clamp (1; 20) for an orthopaedic external fixation system (200; 300) comprising: - a first coupling element (2; 21), comprising a pair of opposite jaws (3, 4; 22, 23) together defining one or more seats able to house at least a first component of the orthopaedic external fixation system (200; 300); - a second coupling element (8; 31), comprising a pair of opposite jaws (9, 10; 33, 34) together defining one or more seats able to house at least a second component of the orthopaedic external fixation system (200; 300); - an interconnection pin (7; 24) that passes through and connects the first (2; 21) and second (8; 31) coupling elements along a main axis of rotation (x; x"); - fastening means arranged to bring the clamp (1; 20) from a slack configuration, in which the first (2; 21) and second coupling elements (8; 31) are relatively rotatable at least along the main axis of rotation (x; x"), to a locked configuration, in which the first (2; 21) and second coupling elements (8; 31) are relatively integral with each other; wherein said fastening means comprise: - temporary fastening means, manually operable, arranged to temporarily bring the clamp (1; 20) in the locked configuration; - definitive fastening means, operable by means of a fastening tool, arranged to definitively bring the clamp (1; 20) in the locked configuration, wherein said temporary fastening means comprise a fastening ring nut (14; 35) arranged to fasten together the first (2; 21) and second coupling elements (8; 31) along the interconnection pin (7; 24), characterized in that said definitive fastening means comprise an eccentric body (12; 28), rotatably mounted on a hinging body that is axially integral with either one of the first (2; 21) or of the second coupling elements (8; 31), said eccentric body (12; 28) passing through a connecting rod head of the interconnection pin (7; 24) along an axis that is perpendicular to the main axis of rotation (x), the opposite end of said interconnection pin (7, 24) being constrained to the other of the first (2; 21) and second coupling elements (8; 31), the rotation of said eccentric body (12; 28) with respect to the hinging body promoting a translation of the opposite end of the interconnection pin (7; 24) towards said hinging body and as a result relatively bringing the two coupling elements (2, 8; 21, 31) nearer each other. - a first coupling element (2; 21), comprising a pair of opposite jaws (3, 4; 22, 23) together defining one or more seats able to house at least a first component of the orthopaedic external fixation system (200; 300); - a second coupling element (8; 31), comprising a pair of opposite jaws (9, 10; 33, 34) together defining one or more seats able to house at least a second component of the orthopaedic external fixation system (200; 300); - an interconnection pin (7; 24) that passes through and connects the first (2; 21) and second (8; 31) coupling elements along a main axis of rotation (x; x"); - fastening means arranged to bring the clamp (1; 20) from a slack configuration, in which the first (2; 21) and second coupling elements (8; 31) are relatively rotatable at least along the main axis of rotation (x; x"), to a locked configuration, in which the first (2; 21) and second coupling elements (8; 31) are relatively integral with each other; - temporary fastening means, manually operable, arranged to temporarily bring the clamp (1; 20) in the locked configuration; - definitive fastening means, operable by means of a fastening tool, arranged to definitively bring the clamp (1; 20) in the locked configuration, wherein said temporary fastening means comprise a fastening ring nut (14; 35) arranged to fasten together the first (2; 21) and second coupling elements (8; 31) along the interconnection pin (7; 24), characterized in that said definitive fastening means comprise an eccentric body (12; 28), rotatably mounted on a hinging body that is axially integral with either one of the first (2; 21) or of the second coupling elements (8; 31), said eccentric body (12; 28) passing through a connecting rod head of the interconnection pin (7; 24) along an axis that is perpendicular to the main axis of rotation (x), the opposite end of said interconnection pin (7, 24) being constrained to the other of the first (2; 21) and second coupling elements (8; 31), the rotation of said eccentric body (12; 28) with respect to the hinging body promoting a translation of the opposite end of the interconnection pin (7; 24) towards said hinging body and as a result relatively bringing the two coupling elements (2, 8; 21, 31) nearer each other.