Dinitrogen pentoxide is the chemical compound with the formula N₂O₅. Also known as nitrogen pentoxide, N₂O₅ is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It is an unstable and potentially dangerous oxidizer that once was used as a reagent when dissolved in chloroform for nitrations but has largely been superseded by NO₂BF₄ (nitronium tetrafluoroborate).