Ysgol Uwchradd Llanfyllin High School is a billingual secondary school situated in the Mid-Wales town of Llanfyllin. It currently has around 1000 pupils. The current headteacher is Mr. Carl Mincher.
The school building lies on the grounds of the former Llwyn Hall that was demolished. The school was built in the 1950s to replace an earlier building and was considerably extended in the early 1970s. The school completed a £2.2 million extension and remodelling programme in 1998 providing a high standard of accommodation and resources.
In 2009, the school took part in an Estyn inspection and received the rating "outstanding".