Collective migration of cells plays an important role in tissue morphogenesis of the developing embryo, wound healing and cancer invasion. In this talk I am going to review briefly mathematical models developed for studying the migration of animal groups (flocks, swarms etc.) and then discuss the application and extension of these results to cell migration. I am going to show that local contact-based cell interactions are sufficient for producing coherent collective motion with similar characteristics to animal groups, and will discuss the role of biologically relevant factors that may influence the migration pattern. Then I will discuss collective navigation of cells in the presence of chemical gradients and show that the accuracy of migration is determined by the collective interactions and is almost independent of the ability of individual cells to detect and follow these gradients.