The Icon widget in Flutter is used to display an icon on the screen. It is a StatelessWidget and can be used in both Stateful and Stateless widgets. The Icon widget is typically used with the IconButton widget to create clickable icons that perform some action. The Icon widget takes a required icon parameter, which specifies the icon to be displayed. The icon can be specified using an Icons class constant or a custom icon defined using the IconData class. The size parameter can also be used to adjust the size of the icon.