Ṭā Hā (/ˈtɑːˈhɑː/; Arabic: طه) is the 20th chapter (sūrah) of the Qur'an with 135 verses (āyāt). It is named "Ṭā Hā" because the chapter starts with the Arabic ḥurūf muqaṭṭaʿāt (disjoined letters) طه (Ṭāhā), which is widely mistaken to be one of the names of the Islamic prophet Muhammad, but is just one of the many unlinked letters at the beginning of many other surahs of the Quran.

Regarding the timing and contextual background of the revelation (asbāb al-nuzūl), it is traditionally believed to be a Meccan surah, from the second Meccan period (615-619), which means it is believed to have been revealed in Mecca, rather than later in Medina.

Among the subjects treated in this chapter are God's call of Moses (Quran 20:10), the Exodus of the Israelites and the crossing of the Red Sea (20:77), the worship of the Golden Calf (20:88) and the Fall of Man (20:120). The main theme of the chapter is about the existence of God. It addresses this theme through stories about Moses and Adam. Sura 20 displays several thematic and stylistic patterns described by Angelika Neuwirth in Jane McAuliffe's book "The Cambridge Companion to the Qur'an". These include the eschatological prophecies of the Quran, signs of God's existence, and debate. Additionally, sura 20 employs what has been termed the "ring structure" to reinforce its central theme.

This is the chapter that convinced Umar to convert to Islam.

The oldest surviving manuscript containing chapter Ṭā Hā is a Quranic manuscript in the Mingana Collection identified as having been written on the Birmingham Quran manuscript, dated 0-25 AH.

The first two words of Chapter 20 are Ṭā Hā.

Sura 20 focuses upon one theme, and is structured in such a way as to reinforce this theme repeatedly. Sura 20 begins with an introduction which proclaims the greatness of God. In the body of the sura, there are two distinct stories, one about Moses and one about Adam, each of which is broken into smaller sections. Both stories are prefaced by instructions from God to Muhammad, and followed by a discussion of judgment day and the punishment of the disbelievers. To conclude the sura, there is another section restating and reinforcing the main theme, followed by a brief instruction to Muhammad. This repetitive pattern is what Carl W. Ernst terms the ring structure in his book "How to Read the Qur'an". The first part of the sura, up until the story of Adam, and the second part are, thematically and structurally, copies of each other. The story about Moses gives a much longer, more detailed description to introduce the theme, and the shorter story of Adam serves to summarize and repeat the theme already discussed. The introduction and conclusion paragraphs, including the verses where God addresses Muhammad, are the bookends to the sura, and bind the stories together.

This section is an introduction to the sura. It begins with God addressing Muhammad, then lists several of God's characteristics and praises Him. In this section, there is also a mention of the Quran as a reminder of God's existence, a theme that is seen throughout the Quran. One of the two verses in this sura mentioned in al-Wahidi's "Asbab al-Nuzul" is verse 2. According to al-Wahidi, God sent this verse to Muhammad because the Quraysh were saying that Muhammad was distressed because he left their religion, and that God only sent down the Quran to distress Muhammad.