Tremeirchion (previously known as Lleweni) is a small residential community in Denbighshire, Wales.

It briefly became well known during the fin de siècle after a series of dinosaur bones were found in the area.

In the 2001 Census, Tremeirchion Ward had a population of 1,589 people,[2] although the civil parish figure for the community was 636.

The community is served by a small Welsh medium primary school, Ysgol Tremeirchion.

According to the latest Estyn inspection report in 2018, there are 73 pupils between three and eleven years old on roll, including 12 part-time nursery age children.