[vram22]

Ruby has a Tk-based one too, but I don't remember the name, since I used it only a little, years ago, though I did some non-GUI Ruby and Rails web work.

[beeburrt]

RubyMotion?

http://www.rubymotion.com/

[vram22]

No, I think it had a bundled one like Python's Tkinter, which was a wrapper over Tcl's Tk.

Edit: this is it, Ruby Tk.

https://ruby-doc.com/docs/ProgrammingRuby/html/ext_tk.html