The magnetized Galactic interstellar medium has become a main hindrance in the analysis of cosmological data. Galactic foregrounds are an issue in different observational contexts for the Cosmic Microwave Background (CMB), the HI 21cm signal from the epoch of reionization (EoR), line intensity mapping and lensing surveys. Galactic magnetic fields also upset the identification of sources of ultra-high energy cosmic rays and the measurement of extragalactic magnetic fields. In each context, cosmology is tied to Galactic astrophysics, and from a methodological point of view, to mathematics, because novel methods are required to model and reproduce the statistical properties of Galactic foregrounds and account for their complexity in the statistical inference of cosmological parameters. The meeting aims at bringing together scientists from Cosmology, Galactic Astrophysics and Mathematics for cross-fertilization. These three themes will be developed in parallel along the week in the context of CMB, large scale structure, EoR, cosmic magnetism and cosmic-ray science and experiments.