| Brennilis | |
| Native Name: | Brenniliz |
| Commune Status: | Commune |
| Coordinates: | 48.3583°N -3.8497°W |
| Insee: | 29018 |
| Postal Code: | 29690 |
| Arrondissement: | Châteaulin |
| Canton: | Carhaix-Plouguer |
| Mayor: | Alexis Manac'h[1] |
| Term: | 2020 - 2026 |
| Intercommunality: | Monts d'Arrée Communauté |
| Elevation Min M: | 149 |
| Elevation Max M: | 278 |
| Area Km2: | 18.69 |
Brennilis (pronounced as /fr/;) is a commune in the Finistère department of Brittany in northwestern France.
Brennilis has an oceanic climate (Köppen climate classification Cfb). The average annual temperature in Brennilis is . The average annual rainfall is with January as the wettest month. The temperatures are highest on average in July, at around, and lowest in February, at around . The highest temperature ever recorded in Brennilis was on 8 August 2003; the coldest temperature ever recorded was on 12 January 1987.
Inhabitants of Brennilis are called Brennilisiens in French.