A camshaft for a multi-cylinder internal combustion engine with poppet valves, comprising a main body, which is rotatable with respect to a first rotation axis, a first disk and means for varying the timing of said first disk with respect to said main body; wherein said main body is shaped so as to define a circuit for a pressurized fluid; wherein said camshaft comprises first thrust means and second thrust means, which are adapted to be operated by said pressurized fluid and translated along respective translation directions, said first and said second thrust means (20, 30) being adapted to engage, on thrust, a first counterpart and a second counterpart, respectively, of said first disk; wherein the engagement on thrust of said first counterpart by said first thrust means and of said second counterpart by said second thrust means, respectively, results in said first disk being rotated with respect to a first rotation axis (R-R) in a first rotation direction and in a second rotation direction, respectively, opposed to said first rotation direction, and therefore, in the relative angle between said first disk and said main body being varied; wherein said main body comprises an internal cavity for collecting the pressurized fluid and a first pipe for conveying the pressurized fluid exiting said internal cavity towards said first thrust means and second thrust means, wherein a switch is housed in said first pipe, which is movable between a first position and a second position, and wherein, when said switch is in said first position, said second thrust means are operated by the pressurized fluid and engage, on thrust, said second counterpart, while when said switch is in said second position, said first thrust means are operated by the pressurized fluid and engage, on thrust, said first counterpart; characterized in that said switch is translatable by centrifugal force along a radial direction to said first rotation axis depending on the angular speed of said main body. wherein said main body is shaped so as to define a circuit for a pressurized fluid; wherein said camshaft comprises first thrust means and second thrust means, which are adapted to be operated by said pressurized fluid and translated along respective translation directions, said first and said second thrust means (20, 30) being adapted to engage, on thrust, a first counterpart and a second counterpart, respectively, of said first disk; wherein the engagement on thrust of said first counterpart by said first thrust means and of said second counterpart by said second thrust means, respectively, results in said first disk being rotated with respect to a first rotation axis (R-R) in a first rotation direction and in a second rotation direction, respectively, opposed to said first rotation direction, and therefore, in the relative angle between said first disk and said main body being varied; wherein said main body comprises an internal cavity for collecting the pressurized fluid and a first pipe for conveying the pressurized fluid exiting said internal cavity towards said first thrust means and second thrust means, wherein a switch is housed in said first pipe, which is movable between a first position and a second position, and wherein, when said switch is in said first position, said second thrust means are operated by the pressurized fluid and engage, on thrust, said second counterpart, while when said switch is in said second position, said first thrust means are operated by the pressurized fluid and engage, on thrust, said first counterpart; characterized in that said switch is translatable by centrifugal force along a radial direction to said first rotation axis depending on the angular speed of said main body.