MODYLAS is a highly parallelized general-purpose molecular dynamics (MD) simulation program appropriate for very large physical, chemical, and biological systems. It is equipped most standard MD techniques including free energy calculations based on thermodynamic integration method. Long-range forces are evaluated rigorously by the fast multipole method (FMM) without using the fast Fourier transform (FFT) in order to realize excellent scalability. The program enables investigations of large-scale real systems such as viruses, liposomes, assemblies of proteins and micelles, and polymers. It works on ordinary linux machines, too.