The Casa Matemática Oaxaca (CMO) will host the "Geometrical Tools for String Cosmology" workshop in Oaxaca, from April 28, 2019 to May 3, 2019. In the past decades, string theory and supergravity have evolved to provide a robust mathematical framework for phenomenological studies of physics. At the same time, cosmology has emerged as a precision science, where observations of the Cosmic Microwave Background and Large Scale Structure pinpoints our Universe as being dominated by dark energy, which causes its accelerated expansion, having a large fraction of dark matter, and very likely having undergone a period of inflation at early times. Yet, we are still at the beginning of precision measurements, and more information will come from future observations, including those in the new area of gravitational wave astronomy and dark matter searches. Therefore, we need clear advances on the theoretical side of cosmology in order to understand, and make testable predictions. The aim of the workshop will be to bring together international experts working on cosmology, supergravity and string theory to provide a solid mathematical and theoretical foundation for the description of the early Universe.