Marburgviruses (Marburg virus and Ravn virus) have caused ~20 outbreaks of human Marburg virus disease since their discovery in 1967. These zoonotic viruses are categorized as priority pathogens with no licensed vaccines or treatment options. The foundation for all experimental work including deciphering disease parameters and countermeasure development is a defined virus stock. This chapter provides a guide for the isolation and growth of marburgviruses in tissue culture.