Yā Sīn (Arabic: سورة يس‎) is the 36th 'chapter' of the Qur'an with 83 ayat, and is one of the Meccan suras. The sura focuses on establishing the Qur'an as a divine source, and it warns of the fate of those that mock God's revelations and are stubborn. The sura tells of the punishments that plagued past generations of nonbelievers as a warning to present and future generations. Additionally, the sura reiterates God's sovereignty as exemplified by His creations through signs from nature. The sura ends with arguments in favor of the existence of Resurrection and God's sovereign power. The name of the chapter comes from the two letters of the first verse of the chapter, which has caused much scholarly debate, and which Tafsir al-Jalalayn, a Sunni Tafsir, interprets by saying "God knows best what He means by these.


It has been proposed that Sura Yā Sīn is the "heart of the Qur'an." This comes from the idea that everything has a heart, and that sura Yā Sīn is the “heart of the Qur’an.” Again, the meaning of “the heart” has been the basis of much scholarly discussion. The eloquence of this sura is traditionally regarded as representative of the miraculous nature of the Qur'an. It presents the essential themes of the Qur'an, such as the sovereignty of God, the unlimited power of God as exemplified by His creations, Paradise, the ultimate punishment of nonbelievers, resurrection, the struggle of believers against polytheists and nonbelievers, and the reassurance that the believers are on the right path, among others. Sura Yā Sīn presents the message of the Qur'an in an efficient and powerful manner, with its quick and rhythmic verses.