On Android voice instructions are available in 27 languages: English, Arabic, Chinese (Traditional and Simplified), Czech, Danish, Dutch, Finnish, French, German, Greek, Hindi, Hungarian, Indonesian, Italian, Japanese, Korean, Persian, Polish, Portuguese, Romanian, Russian, Spanish, Thai, Turkish, Ukrainian, Vietnamese.
Google TTS supports all listed languages except of Arabic and Persian (Farsi). For these languages you may need to install third party TTS (for example, eSpeak TTS, Vocalizer TTS or SVOX Classic TTS) and a language pack from app store (Google Play Store, Samsung Apps, etc).
On iOS voice instructions are available in 26 languages: English, Arabic, Chinese (Traditional and Simplified), Czech, Danish, Dutch, Finnish, French, German, Greek, Hindi, Hungarian, Indonesian, Italian, Japanese, Korean, Polish, Portuguese, Romanian, Russian, Slovak, Spanish, Swedish, Thai, Turkish.