P4O7, a new phosphorus oxide, was obtained by reaction of P4O6 with alkali metal oxides A2O. P4O7 has an adamantane‐like structure with one terminal O atom. However, the idea that these molecules are constructed, in a building‐block manner, from P4O6 and P4O10 units, with retention of the PO bond lengths is not entirely reconcilable with the structural findings.