钻纹龟（学名：Malaclemys terrapin）又名菱斑龟、金刚背泥龟，龟鳖目泽龟科鸡龟亚科属下物种，原产自美国东部及南部临汽水海域的沼泽。这种龟是一种单型物种，属于钻纹龟属（Malaclemys）。

种加词“terrapin”是来源于阿尔冈昆语族的torope。“Terrapin”在英式英语和美式英语都用于表示Malaclemys terrapin的简称。这种用法源于早期北美的欧洲殖民者描述这种汽水水域的龟，因为这种龟既不栖息于淡水水域，也不见于海中。现在美语中仍旧保存这种用法，仅指钻纹龟，但在英式英语中terrapin也可指代其他半水生的龟，如红耳龟。

The diamondback terrapin (Malaclemys terrapin) or simply terrapin, is a species of turtle native to the brackish coastal swamps of the eastern and southern United States. It belongs to the monotypic genus, Malaclemys. It has one of the largest ranges of all turtles in North America, stretching as far south as Florida Keys and as far north as Cape Cod.