Bleddyn is a masculine, Welsh given name.
Other spellings of Bleddyn are: Blevin, Blevyn, Blethyn, Blethin, Blevins, Blethins, Blethyns, Plethyn, Plethin, Pleddyn, Plethin and many others.
List of bearers include:
- Bleddyn ap Cynfyn (died 1075), Prince of the Welsh Kingdoms of Gwynedd and of Powys
- Bleddyn Bowen (born 1961), former international Wales rugby union player
- Bleddyn Fardd (1258–1284), Welsh-language court poet from Gwynedd
- Bleddyn Taylor (born 1959), Welsh rugby union player
- Bleddyn Williams MBE (born 1923), Welsh rugby union centre
- Cadwgan ap Bleddyn (1051–1111), prince of Powys in eastern Wales
- Iorwerth ap Bleddyn (1053–1111), prince of Powys in eastern Wales
- Maredudd ap Bleddyn (1047–1132), prince of Powys in eastern Wales
- Rhiryd ap Bleddyn (1049–1088), Welsh king of Powys
- Bleddyn Môn (born 1991), Welsh sailor - America's Cup, Volvo Ocean Race and Extreme Sailing Series competitor