Electron fractionalization is of significant interest to both fundamental physics and topological quantum computing. The emergence of two-dimensional moiré materials provides a platform to explore the physics of electron fractionalization under zero magnetic field. In this talk, I will discuss two examples of zero-field electron fractionalization in moiré semiconductors: 1) the fractional Chern insulator that spontaneously breaks the time reversal symmetry, and 2) the time reversal symmetric fractional quantum spin Hall insulator.