Keywords:Fokker-Planck equations Non-Gaussian white noise Lévy processes Marcus stochastic differential equations Probability density function for solution Fokker-Planck equations describe time evolution of probability densities of stochastic dynamical systems and play an important role in quantifying propagation and evolution of uncertainty. Although Fokker-Planck equations can be written explicitly for systems excited by Gaussian white noise, they have remained unknown in general for systems excited by multiplicative non-Gaussian white noise. In this paper, we derive explicit forms of Fokker-Planck equations for one dimensional systems modeled by Marcus stochastic differential equations under multiplicative non-Gaussian white noise. As examples to illustrate the theoretical results, the derived formula is used to obtain Fokker-Planck equations for nonlinear dynamical systems under excitation of (i) α-stable white noise; (ii) combined Gaussian and Poisson white noise, respectively.