购买力平价（英语：Purchasing Power Parity，缩写PPP），又称相对购买力指标，是一种根据各国不同的价格水平计算出来的货币之间的等值系数，使我们能够在经济学上对各国的国内生产总值进行合理比较，这种理论汇率与实际汇率可能有很大的差距。购买力平价计算单位为国际元（international dollar，缩写：Intl.$）或称作“国际货币单位”（international currency unit，缩写：ICU）。购买力平价是以美元为基础，即1美元在美国的购买力为参考基数；故1国际元在个别国家的购买力等于1美元在美国的购买力，因此很多情况下，购买力平价直接使用US$计价。

Theories that invoke purchasing power parity assume that in some circumstances (for example, as a long-run tendency) it would cost exactly the same number of, for example, US dollars to buy euros and then to use the proceeds to buy a market basket of goods as it would cost to use those dollars directly in purchasing the market basket of goods.