The Quark Matter 2014 conference is the twenty-fourth edition of the most prestigious series of international meetings in the field of ultrarelativistic heavy-ion collisions. The meetings bring together theorists and experimentalists committed to understanding the fundamental properties of strongly interacting matter at extreme energy densities. The conditions reached in head-on nuclear collisions at the highest currently available energies correspond to those in primordial matter a few tens of microseconds after the Big Bang. Thus, this type of laboratory research improves our understanding of the early phase of the Universe. The first Quark Matter conference took place in 1980 in Darmstadt. Since then, the meetings of this series have been organized approximately every 1.5 years. The recent instances were in Jaipur, India (2008), Knoxville, USA (2009), Annecy, France (2011), and Washington DC, USA (2012). The current meeting brings the conference to Darmstadt again, a place with a long-standing tradition of heavy-ion research.