In this review, synthesis, analytical properties and reactivity as well as theoretical studies of σ3λ3-oxaphosphiranes κP-carbonylmetal(0) complexes A, are presented. Furthermore, epoxide-like chemistry and other, more phosphorus-specific reactivity features will be discussed in detail. Display omitted In this review, the chemistry of σ3λ3-oxaphosphirane metal complexes is presented which was developed over the last 30 years. Important aspects like the improvements in the synthetic accessibility, starting from epoxidation of phosphaalkene complexes in the early 90s to the usage of Li/Cl phosphinidenoid complexes in formal 2+1 cycloaddition reactions with aldehydes and ketones are discussed. Furthermore, physical properties, depending on the P-substituent and metal fragment, as well as the results of quantum chemical calculations are presented, with a special focus on the ring strain energy. The existence of three different polar bonds in the oxaphosphirane ligand open a great variety of synthetic opportunities such as the use of these metal complexes in ring rearrangements, ring expansions catalyzed by strong Brønsted acids, ring opening reactions with protic substrates giving access to 1,2-difunctional phosphane complexes or “ring deconstruction” with different nucleophiles.