The Trionychidae are a taxonomic family of a number of turtle genera, commonly known as softshell turtles. The family was erected by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can adapt to living in highly brackish areas. Members of this family occur in Africa, Asia, and North America, with extinct species known from Australia. Most species have traditionally been included in the genus Trionyx, but the vast majority have since been moved to other genera. Among these are the North American Apalone softshells that were placed in Trionyx until 1987.

Turtles, or testudines, are reptiles of the order Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira and Cryptodira, which differ in the way the head retracts. There are 360 living and recently extinct species of turtles, including land-dwelling tortoises and freshwater terrapins. They are found on most continents, some islands and, in the case of sea turtles, much of the ocean. Like other amniotes they breathe air and do not lay eggs underwater, although many species live in or around water.