The Quran is the word of God, the Creator of all mankind. As such, the Quran is revealed for all mankind to understand. This is why Muslim scholars, the Ulama, have held the translation of the Quran to be lawful, for those who do not know the Arabic language. Because according to the principle of Islamic fiqh, if something is obligatory (for example understanding the Quran) and cannot be performed without another thing (translation of the Quran in one’s understandable language), then the second thing also becomes obligatory. Translation of the Quran into any language is simply a translation; it is not a substitute for the text of the Quran. If someone claimed that his translation was a substitute for the Quranic text, then that would be objectionable. When the Arabic text is intact, there is no possibility that people would consider a translation to be the Quran itself, so the translation of the Quran is quite permissible if done for the purpose of acquainting those who have no access to the Arabic language with the message of the Quran.

Source: The Quran Introduction