当日冲销，简称当冲，是证券市场上的一种交易行为。在香港称为即日买卖、Day trading、即日鲜，在中国大陆称为日内交易，在**称为当日冲销、当冲。

指的是为了从当日证券或商品价格的波动中赚取利润，或是在股票或金融激活市场上买进或卖出后，为了避免价格波动的风险，在当天进行抛补以轧平头寸，而在同一日买进及卖出同一档金融商品的投机式交易。会以当日冲销方式进行的大多是股票、期货、选择权、外汇等。使用这种交易方式的投资者常被称为「当冲客」（day trader）。

Day trading is speculation in securities, specifically buying and selling financial instruments within the same trading day. Strictly, day trading is trading only within a day, such that all positions are closed before the market closes for the trading day. Many traders may not be so strict or may have day trading as one component of an overall strategy. Traders who participate in day trading are called day traders. Traders who trade in this capacity with the motive of profit are therefore speculators.