Beautiful Names of Allah

According to a hadith, there are at least 99 names of God in Islam, known as the ʾasmāʾu llāhi l-ḥusnā (Arabic: أسماء الله الحسنى‎ Beautiful Names of God). The names are also called 99 Attributes of Allah, which are revealed by Allah himself in the Quran.

According to Sahih Bukhari Hadith

Abu Hurairah reported that Allah has ninety-nine Names, i.e., one hundred minus one, and whoever believes in their meanings and acts accordingly, will enter Paradise; and Allah is witr (one) and loves 'the witr' (i.e., odd numbers).

— Sahih Bukhari - Vol. 8, Book 75, Hadith 419 

There's another Sahih Muslim Hadith 

Allah's Messenger (ﷺ) said, "Allah has ninety-nine Names, one-hundred less one; and he who memorized them all by heart will enter Paradise." To count something means to know it by heart.

— Sahih Bukhari - Vol. 9, Book 93, Hadith 489

The Qur'an refers to God's Most Beautiful Names (al-ʾasmāʾ al-ḥusná) in several Surahs. Gerhard Böwering refers to Surah 17 (17:110) as the locus classicus to which explicit lists of 99 names used to be attached in tafsir. A cluster of more than a dozen Divine epithets which are included in such lists is found in Surah 59. Mystic philosopher Ibn Arabi surmised that the 99 names are "outward signs of the universe's inner mysteries".