We present the most general rotating black hole solution of five-dimensional N = 4 superstring vacua that conforms to the no-hair theorem . It is chosen to be parameterized in terms of massless fields of the toroidally compactified heterotic string. The solutions are obtained by performing a subset of O(8,24) transformations, i.e. symmetry transformations of the effective three-dimensional action for stationary solutions, on the five-dimensional (neutral) rotating solution parameterized by the mass m and two rotational parameters l 1 and l 2 . The explicit form of the generating solution is determined by three SO(1, 1) O(8, 24) boosts, which specify two electric charges Q ( 1 ) 1 , Q ( 2 ) 2 of the Kaluza-Klein and two-form U(1) gauge fields associated with the same compactified direction, and the charge Q (electric charge of the vector field, whose field strength is dual to the field strength of the five-dimensional two-form field). The general solution, parameterized by 27 charges, two rotational parameters and the ADM mass compatible with the Bogomol'nyi bound, is obtained by imposing [SO(5) SO(21)][SO(4) SO(20)] O (5,21) transformations, which do not affect the five-dimensional space-time. We also analyze the deviations from the BPS-saturated limit.