在会计学中，复式簿记（又称为复式记账法）是商业及其他组织上记录金融交易的标准系统。现代复式簿记系统是由意大利数学家卢卡·帕西奥利，在他的《Summa de arithmetica, geometrica, proportioni et proportionalità》（1494年于威尼斯）一书中最早制定。前提是商业（或其他组织）的财务状况和经营业绩在帐户中被很好地记录。每个帐户记录了某一方面业务货币价值变化的“历史”。

该系统之所以称为复式簿记，是因为每笔交易都至少记录在两个不同的账户当中。每笔交易的结果至少被记录在一个借方和一个贷方的账户，且该笔交易的借贷双方总额相等。

Double-entry bookkeeping, in accounting, is a system of bookkeeping so named because every entry to an account requires a corresponding and opposite entry to a different account. For instance, recording earnings of $100 would require making two entries: a debit entry of $100 to an account called "Cash" and a credit entry to an account called "Revenue."