Summary: We propose a relativistically invariant wave equation for the Skyrme soliton. It is a differential equation on the space \(\mathbb R^{1,3}\times S^{3}\) which is invariant under the Lorentz group and isospin. The internal variable valued in \(SU(2)\equiv S^{3}\) describes the orientation of the soliton. The mass of a particle of spin and isospin both equal to \(j= \frac 1 2 , \frac 3 2 , \dots \) is predicted to be \(M = m\sqrt{\frac{1+K_2j(j+1)}{1+K_1j(j+1)}}\) which agrees with the known spectrum for low angular momentum. The iso-scalar magnetic moment is predicted to be \(\frac {-K_1}{43}\Sigma \), where \(\Sigma \) is the spin.