Navigate to: C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\games\Far Cry 3\data_win32\ (or your Steam/Epic equivalent).
Under the tab, select English from the Language selection drop-down. English Language Pack For Far Cry 3
If you own the game on a major platform, the language pack is often handled automatically: English Language Pack For Far Cry 3
You require the English sound and sounds folders from a legitimate English copy of the game. These folders contain the .dat and .fat files required for voice acting. English Language Pack For Far Cry 3
or simply want to change your immersion settings, getting the game into English is a common need. While some versions are region-locked, there are several official and community-tested methods to ensure your subtitles and audio are correctly configured. Official Methods via Ubisoft and Steam