“Al-Kutub al-Sitta” is an expression that is composed of the word ‘kutub’, meaning ‘books’ and ‘sitta’ which means ‘six’; collectively it means -literally- the “six books”.

In the terminology of Islamic sciences, al-Kutub al-Sitta is the name given to the six hadith (sayings of the Prophet) books that contain collections of the most authentic (reliable) hadiths; these constitute the content of the prophetic sunnah (practices of the Prophet), one of the two most important sources of the Islamic religion (the other being the Quran). These six books include the two works by al-Bukhari and Muslim in the genre of the Jami al-Sahih, which are accepted as the second most authentic books after the Quran, as well as the four books in the genre of the Sunan that belong to Abu Davud, Tirmidhi, Nasaai, and Ibn Majah.

Although some scholars list the books by Imam Malik and Darimi in place of that by Ibn Majah among al-Kutub al-Sitta, Ibn Majah's book has usually been accepted as the sixth of al-Kutub al-Sitta by the majority of hadith scholars.