Quark-gluon plasma (abbreviation QGP) is a state of matter at extremely high temperatures or baryon densities. Here, the confinement of quarks and gluons is lifted, which is why these particles exhibit quasi-free behavior. In English-speaking countries, particle physicists use the humorous term “quark soup.”

It is assumed that the universe went through this state in the first fractions of a second after the Big Bang. In today's universe, the QGP exists at most in the center of neutron stars, although some theories predict a further phase there, which is said to be characterized by color superconductivity.