The Fifteenth Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Astrophysics and Relativistic Field Theories (MG15) will take place at "La Sapienza" University in Rome, Italy from July 1 to 7, 2018. Registration will take place on Sunday July 1, from 10am to 7pm at Sapienza University. During this six day conference, a variety of topics will be discussed in the morning plenary sessions with preliminary schedule, beginning with Mathematical Topics on Monday, Quantum and Gravity on Tuesday, Gravitational Waves on Wednesday, GRBs and Galactic Center Black Holes on Thursday, Cosmology and Space Science on Friday and The Frontiers on Saturday. There will be six plenary lectures each morning and up to twenty parallel sessions in the four weekday afternoons excluding Wednesday, which is left free for a trip and the evening conference banquet.