The discovery, recent developments and prospects of the carbeniophosphines, and in particular of imidazoliophosphines, are related. The P-conjugated positive charge brought by the stabilized carbenium center gives stable (Im+)R2P → metal dative bonds, while the ligands themselves contain a relatively stable C → P+R2 dative bond, making imidazoliophosphines, more accurately described as NHC–phosphenium adducts. The preparation methods, structural features, electronic and coordination properties, reactivity, and catalytic properties of carbeniophosphines are reviewed.