MBS：Mortgage-Backed Security， 抵押支持债券或者抵押贷款证券化。In finance, a mortgage-backed security (MBS) is an asset-backed security whose cash flows are backed by the principal and interest payments of a set of mortgage loans. Payments are typically made monthly over the lifetime of the underlying loans.

其基本结构是，把贷出的住房抵押贷款中符合一定条件的贷款集中起来，形成一个抵押贷款的集合体（pool），利用贷款集合体定期发生的本金及利息的现金流入发行证券，并由政府机构或政府背景的金融机构对该证券进行担保。因此，美国的MBS实际上是一种具有浓厚的公共金融政策色彩的证券化商品。