Moderation is linked to all aspects of the life of individuals in the Islamic societies, but its meanings vary in terms of language and terminology due to the diversity and expansion of the Arabic language, as well as the fact that meanings of moderation in Islam vary based on the use of the word in Quran and Sunna. Sometimes we see that moderation means justice, or adopting a middle position, and other times it means balance, as well as preference and beauty, and finally it could be used in the temporal and spatial structure. It was therefore necessary to delve into explaining the meaning of moderation in language and terminology, and to deepen the meanings of moderation in Islam, through an analytical descriptive approach based on the review and analysis of the most important Quranic verses and prophetic traditions that explain moderation in Islam and its foundations, in addition to the discussion and analysis of previous studies related to the subject. After clarifying and detailing the various meanings of moderation in the language and terminology, Quran and Sunnah, this study highlights the importance and status of moderation in Islam, and how it is represented in a good manner. It is a key to understanding Islam, its wisdom and meanings. It also evaluates the behavior of the individual among the good or the bad, or the best of two evils. Misinterpretation of moderation may occur by misunderstanding it as an invitation to indulgence and modesty. It was therefore necessary that this study seek to highlight the role of the Holy Quran and the Sunna in establishing the features of moderation and explaining its determinants and rules. The researcher hopes that this study will contribute to providing libraries with an important study on the legalization of moderation in the Holy Quran and Sunnah. The study concludes that moderation in Islam includes charity, justice, and facilitation, and not exposing anybody to embarrassment. It means wisdom, uprightness, and intimacy. It is a beacon that shuns all meanings of excessive and trivial understandings. Thus, the moderation of Islam is a fair, virtuous, and separate distinction between good and evil, and leads to a balance between the spiritual and material, the individual and collective, and realism and idealism.