| Merdrignac | |
| Native Name: | Medrigneg |
| Commune Status: | Commune |
| Image Flag: | Flag of Merdrignac.svg |
| Image Coat Of Arms: | CoA fr Merdrignac.svg |
| Coordinates: | 48.1933°N -2.4131°W |
| Insee: | 22147 |
| Postal Code: | 22230 |
| Arrondissement: | Saint-Brieuc |
| Canton: | Broons |
| Mayor: | Eric Robin[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | Loudéac Communauté - Bretagne Centre |
| Elevation Min M: | 77 |
| Elevation Max M: | 196 |
| Area Km2: | 57.12 |
Merdrignac (in French pronounced as /mɛʁdʁiɲak/;) is a commune in the Côtes-d'Armor department of Brittany in northwestern France.
The River Meu forms most of the commune's northern border.
Merdrignac has an oceanic climate (Köppen climate classification Cfb). The average annual temperature in Merdrignac is . The average annual rainfall is with December as the wettest month. The temperatures are highest on average in July, at around, and lowest in December, at around . The highest temperature ever recorded in Merdrignac was on 5 August 2003; the coldest temperature ever recorded was on 12 January 2010.
Inhabitants of Merdrignac are called merdrignaciens in French.