In the current chapter we provide a catalog of functional groups containing the chalcogens selenium and tellurium where by functional group we mean the central atom, Se or Te, and its local arrangement of atoms bonded to it by single or multiple bonds (its neighborhood). We will do so by cataloging examples of compounds containing the groups. The atoms that define the local neighborhood are limited here to H, C, N, the chalcogens O, S, Se, Te, and the halogens F, Cl, Br and I. As such we avoid Se‐ and Te‐bonding to metals and metalloids and so we will ignore all salts, and we also ignore all groups with formal charges. However arbitrarily, we did include complexes involving species wherein, with appropriate bond‐shifting, we can draw the compound of interest without any formal charges. We have also avoided mention of free radicals and other species with unpaired electrons. All of the groups were explicitly chosen, and have at least one carbon attached to the selenium or tellurium. For each group we generally give one compound as an example (admittedly our choice of name is often unsystematic), a reference to the primary literature (again chosen unsystematically), and the CAS RN for the example compound (when available). Where there is no example we will generally explicitly say so, occasionally with due annotation as NO CAS RN or “no compounds identified” to encourage their study.