Tk may refer to any of the following:
1. Short for toolkit, Tk is a library of GUI elements that was developed by John Ousterhout, and included with Tcl to help promote and allow for the development of a GUI interface. Today, other languages such as Perl include their own Tk, which is in part or all of the Tcl/Tk libraries.
2. .tk is also a domain suffix for Tokelau.