Nowadays, designing and searching for materials with multiple functional characteristics are the keys to achieving high-performance electronic devices. Among many candidates, two-dimensional multiferroic materials have great potential to be applied in highly integrated magnetoelectric devices, such as high-density non-volatile memories. Here, we predict a two-dimensional material, VOF2 monolayer, to possess intrinsic ferroelectric and ferromagnetic properties. The VOF2 monolayer owns the largest in-plane ferroelectric polarization (332 pC m-1) in the family of VOX2 (X: halogen) oxyhalides. Different from other VOX2 monolayers whose magnetic ground states are antiferromagnetic or noncollinear spiral textures, the VOF2 monolayer owns a robust ferromagnetic ground state, which is rare but highly desirable. Our theoretical prediction provides a good candidate and starting point for the further pursuit of more two-dimensional multiferroic materials with high-performance magnetoelectricity.