Since 1975, the Marcel Grossmann Meetings (on Recent Developments in Theoretical and Experimental General Relativity, Gravitation, and Relativistic Field Theories) have been organized in order to provide opportunities for discussing recent advances in gravitation, general relativity and relativistic field theories, emphasizing mathematical foundations, physical predictions and experimental tests. The objective of these meetings is to elicit exchange among scientists that may deepen our understanding of spacetime structures as well as to review the status of ongoing experiments aimed at testing Einstein's theory of gravitation either from the ground or from space. Previous meetings have been held in Trieste (MG1: 1975) and (MG2: 1979), Shanghai (MG3: 1982), Rome (MG4: 1985, MG9: 2000), Perth (MG5: 1988), Kyoto (MG6: 1991), Stanford (MG7: 1994), Jerusalem (MG8: 1997), Rio (MG10: 2003), Berlin (MG11: 2006), Paris (MG12: 2009), Stockholm (MG13: 2012), MG14 in 2015 and MG15 in 2018 both in Rome.