银行存款准备金比率（Required Reserve Ratio，也译作存款准备金比率、现金准备比例、准备金比例、准备金要求、存款准备率），指商业银行的初级存款中不能用于放贷的部分的比例。

为保障存款人的利益，银行机构不能将吸纳的存款全部用于发放贷款或者是进行炒股票等金融投资，必须保留一定的资金，存放在银行内（如美国）或缴存在中央银行（如中国大陆），以备客户提款的需要，这部分的存款就叫做存款准备金。而存款准备金与存款总额的比例，就是银行存款准备金比率。

Fractional-reserve banking is the practice whereby a bank accepts deposits, makes loans or investments, and holds reserves that are a fraction of its deposit liabilities. Reserves are held at the bank as currency, or as deposits in the bank's accounts at the central bank. Fractional-reserve banking is the current form of banking practiced in most countries worldwide.