Llantysilio () is a community in Denbighshire, Wales, near Llangollen. It had a population of 472 in 2001, falling to 421 at the 2011 census.
The community includes the site of Valle Crucis Abbey, the Horseshoe Pass, and Llantysilio Hall; it also includes the villages of Pentredwr and Rhewl, as well as the areas of Eglwyseg, Llandynan, and Llidiart Annie.
A Topographical Dictionary of Wales (1849) described it as follows: