  The study of entanglement in particle physics has been gathering pace in the
past few years. It is a new field that is providing important results about the
possibility of detecting entanglement and testing Bell inequality at colliders
for final states as diverse as top-quark or $\tau$-lepton pairs, massive gauge
bosons and vector mesons. In this review, after presenting definitions, tools
and basic results that are necessary for understanding these developments, we
summarize the main findings -- as published up to the end of year 2023. These
investigations have been mostly theoretical since the experiments are only now
catching up, with the notable exception of the observation of entanglement in
top-quark pair production at the Large Hadron Collider. We include a detailed
discussion of the results for both qubit and qutrits systems, that is, final
states containing spin one-half and spin one particles. Entanglement has also
been proposed as a new tool to constrain new particles and fields beyond the
Standard Model and we introduce the reader to this promising feature as well.
