Dendritic pyroxene and olivine within intragranular silicate inclusions in natural iron-carbon alloy (~2% C) contain up to 2.7 wt.% P2O5. The pyroxene and olivine crystallized rapidly in supersaturated silicate liquids, enriched in FeO (13–55 wt.%), TiO2 (2–5 wt%), and P2O5 (2–4 wt.%), which were trapped as immiscible liquids within iron-carbon liquid. The structural formulae of the pyroxene and olivine indicate that the P substitutes for Si in these minerals, as predicted from theoretical considerations and consistent with rare, previously reported occurrences of P-rich silicates. In the olivine P+5 appears to be charge-balanced by octahedral site vacancies. In the pyroxenes P+5 is probably charge-balanced by coupled substitution with Al+3 or Ti+3 or by octahedral site vacancies. Three factors could possibly have led to the incorporation of these unusually large amounts of P into the structures of these minerals: 1) the high P2O5 contents, coupled with the low SiO2 contents of the liquids in which they crystallized; 2) rapid crystallization from supersaturated liquids; 3) low ƒO2. Further studies, particularly experimental, are needed to determine quantitatively how these factors affect P silicate crystal/liquid distribution factors. Phosphorus in the upper mantle (except in local regions, metasomatically enriched in P2O5) might occur principally in the structures of pyroxene and olivine, rather than in apatite.