AbstractA key is given to the world genera of the chalcidoid family Aphelinidae. Forty‐four genera are accepted as valid, including three described as new,Encarsiella(type‐speciesE.noyesisp.n.),Hirtaphelinus(type‐speciesH.smetanaisp.n.) andSamariola(type‐speciesS.camerounensissp.n.). The key is followed by a synopsis of the world genera, which includes: (1) citations of valid genera and their synonyms in chronological order; (2) total or approximate number of described species; (3) distribution in the six zoogeographical regions; (4) references mainly to major works and revisions; and (5) comments, especially on the new synonymies introduced in the present paper. The following new synonymies are proposed (the senior synonyms (valid names) are noted in parentheses):AleurodiphilusDeBach&Rose (EncarsiaFoerster);AneristusHoward,AtaneostigmaGirault,HeptacritusDe Santis (CoccophagusWestwood); Artas Howard (Pteroptrix Westwood);PlastocharellaGirault,TurmidiscapusGirault (CentrodoraFoerster);EncyrtophyscusBlanchard,PhysculusJasnosh,PhyscusHoward (CoccobiusRatzeburg);MesidiaFoerster (AphelinusDalman);ParanthemusGirault (CalesHoward);PrimaprospaltellaDeBach&LaSalle (CoccophagoidesGirault). The following genera are regarded as of doubtful position:MesopireneGirault,NeocalesRisbec,PaulianaphelinusRisbec andVereki