二级市场又称次级市场，是买卖已经上市的公司的股票的资本市场。新股发行不属于二级市场。二级市场是任何旧金融商品的交易市场，可为金融商品的最初投资者提供资金的流动性。这里金融商品可以是股票、债券、按揭、人寿保险等。

二级市场在新证券被发行后即存在，有时也被称做「配件市场」（aftermarket）。一旦新发行的证券被列入证券交易所里，也就是做市商（market maker）开始出价和提供新证券之后，投资者和投机客便可以比较轻易地进行买卖交易。

各国的股票市场一般都是二级市场。与美国等西方国家比较，按揭贷款、人寿保险等金融产品的二级市场在中国基本上还没有形成。

The secondary market, also called the aftermarket, is the financial market in which previously issued financial instruments such as stock, bonds, options, and futures are bought and sold. Another frequent usage of "secondary market" is to refer to loans which are sold by a mortgage bank to investors such as Fannie Mae and Freddie Mac.