We are pleased to summarise the IAU Symposium 380, Cosmic Masers: Proper Motion toward the Next-Generation Large Projects held on March 2023 March 20-24 in Kagoshima City, Japan. It is the sixth symposium focusing on astrophysical masers broadly used in research of star formation and evolved stars, astrometric measurements of the Milky Way galaxy, as well as studies of extragalactic environments.