| Country: | Wales |
| Official Name: | Llandysilio |
| Coordinates: | 52.7693°N -3.0852°W |
| Population: | 1,122 |
| Unitary Wales: | Powys |
| Lieutenancy Wales: | Powys |
| Constituency Westminster: | Montgomeryshire |
| Constituency Welsh Assembly: | Montgomeryshire |
| Post Town: | LLANYMYNECH |
| Postcode District: | SY22 |
| Postcode Area: | SY |
| Dial Code: | 01691 |
| Os Grid Reference: | SJ268196 |
| Static Image Name: | Montgomery_Canal_Bridge_No.100_-_geograph.org.uk_-_575421.jpg |
| Static Image Caption: | Montgomery Canal Bridge in Llandysilio |
Llandysilio is a small village and community in Montgomeryshire, Powys, Wales.
Its population at the 2001 Census was 962,[1] increasing to 1,122 at the 2011 census.[2] The present parish church, dedicated to Saint Tysilio, dates from 1867 but tradition states that a church was founded here by Tysilio in the seventh century.[3] The community includes the village of Four Crosses.
Robert Baugh (1748–1832), a Welsh surveyor, copper-plate engraver, map-maker and print-maker came from the town; as did Rev. Elias Owen MA, F.S.A. (1833–1899), a Welsh cleric and antiquarian.
An electoral ward in the same name exists. This ward had a population of 1,789 at the 2011 Census.[4]