- GtkBin - A container with just one child
- GtkBox - Base class for box containers
- GtkButtonBox - Base class for GtkHButtonBox and GtkVButtonBox
- GtkContainer - Base class for widgets which contain other widgets
- GtkItem - Abstract base class for GtkMenuItem, GtkListItem and GtkTreeItem
- GtkMisc - Base class for widgets with alignments and padding
- GtkObject - The base class of the GTK+ type hierarchy
- GtkPaned - Base class for widgets with two adjustable panes
- GtkRange - Base class for widgets which visualize an adjustment
- GtkScale - Base class for GtkHScale and GtkVScale
- GtkScrollbar - Base class for GtkHScrollbar and GtkVScrollbar
- GtkSeparator - Base class for GtkHSeparator and GtkVSeparator
- GtkWidget - Base class for all widgets
- GtkIMContext - Base class for input method contexts
