A headlight structure shaped to be applied to a part of a bicycle, preferably to the tube of the bicycle, said headlight structure comprising: - An attachment portion (1, 1',1a,1b) shaped to be removably connected to said part of the bicycle; - An arm which comprises a first end connected to said attachment portion and a second end on which a light source is arranged; - And wherein said attachment portion is connectable to the said bicycle part through connection means such that said attachment portion is rotatably connected to said bicycle part around at least one rotation axis (X-X), so that said light source can be oriented as a consequence of the rotation of said arm around said at least one rotation axis (X-X), to project a beam of light according to at least two different directions (A, B); Characterized in that: - Said attachment portion is in the shape of a cylindrical T-shaped tubular; - Wherein said connection means provide a couple of cable ties for fixing said cylindrical T-shaped tubular in contact with the said bicycle part, said cable ties being arranged on the opposite part to each other and surrounding said attachment portion and the said bicycle part between each other so that, in use, enabling a frictional rotation between the said attachment portion and the said bicycle part; - And wherein said T-shaped tubular is formed by a first cylindrical tubular with a predetermined longitudinal axis and a predetermined longitudinal length from which a second cylindrical tubular branches off from the cylindrical surface of the first cylindrical tubular at a half of the whole longitudinal length of said first cylindrical tubular, the longitudinal axis of the second cylindrical tubular being orthogonal to the longitudinal axis of said first cylindrical tubular from which it branches off, so as to assume said T-shaped form, the said arm having its first end connected to said second cylindrical tubular. - An attachment portion (1, 1',1a,1b) shaped to be removably connected to said part of the bicycle; - An arm which comprises a first end connected to said attachment portion and a second end on which a light source is arranged; - And wherein said attachment portion is connectable to the said bicycle part through connection means such that said attachment portion is rotatably connected to said bicycle part around at least one rotation axis (X-X), so that said light source can be oriented as a consequence of the rotation of said arm around said at least one rotation axis (X-X), to project a beam of light according to at least two different directions (A, B); - Said attachment portion is in the shape of a cylindrical T-shaped tubular; - Wherein said connection means provide a couple of cable ties for fixing said cylindrical T-shaped tubular in contact with the said bicycle part, said cable ties being arranged on the opposite part to each other and surrounding said attachment portion and the said bicycle part between each other so that, in use, enabling a frictional rotation between the said attachment portion and the said bicycle part; - And wherein said T-shaped tubular is formed by a first cylindrical tubular with a predetermined longitudinal axis and a predetermined longitudinal length from which a second cylindrical tubular branches off from the cylindrical surface of the first cylindrical tubular at a half of the whole longitudinal length of said first cylindrical tubular, the longitudinal axis of the second cylindrical tubular being orthogonal to the longitudinal axis of said first cylindrical tubular from which it branches off, so as to assume said T-shaped form, the said arm having its first end connected to said second cylindrical tubular.