In physics, a Dirac fermion is a fermion which is not its own antiparticle. It is named for Paul Dirac. They can be modelled with the Dirac equation.
The alternative to a Dirac fermion is a Majorana fermion.
In particle physics, all fermions in the standard model, except possibly neutrinos, are Dirac fermions.
In condensed matter physics, low-energy excitations in graphene and topological insulators, among others, are fermionic quasiparticles described by a pseudo-relativistic Dirac equation.