In particle physics, the term particle zoo is used colloquially to describe a relatively extensive list of the known elementary particles that almost look like hundreds of species in the zoo.

The situation was particularly confusing in the late 1960s, before the discovery of quarks, when hundreds of strongly interacting particles (hadrons) were known. It turned out later that they were not elementary but rather composites of the quarks. The set of particles believed today to be elementary is known as the Standard Model.

According to string theory, all particles in the "zoo" have a common ancestor, namely a vibrating string.