What does Islam say about torture?

Human dignity comes from Allah

The Quran states that dignity belongs to every human being, not only to Muslims or to the innocent:

Because that honor is given by Allah, no ruler, soldier or interrogator has the right to strip it away. Even a criminal remains a person with rights. See Is sharia law compatible with human rights?

The Prophet's ﷺ clear warning

A Companion, Hisham ibn Hakim, once passed some people in Syria who had been made to stand in the sun as a punishment over unpaid taxes. He went to the governor and quoted the Prophet ﷺ: "Allah will torment those who torment people in this world." The governor ordered them released (Sahih Muslim 2613).

The Prophet ﷺ even said a woman was punished in the Hereafter because she locked up a cat, neither feeding it nor letting it find food, until it died (Sahih al-Bukhari 3482). If cruelty to an animal is that serious, cruelty to a human being is far worse. See Are animal fighting sports haram?

Forced confessions don't count

The Prophet ﷺ said that Allah has excused his community for mistakes, forgetfulness and what they are forced into (40 Hadith an-Nawawi 39). Building on this, the classical schools (Hanafi, Maliki, Shafi'i and Hanbali) treat a confession under threat or beating as invalid in court. So torture is not only cruel; it also fails as a way to establish the truth.

What about Islamic punishments?

People sometimes confuse torture with the fixed hudud penalties in classical law. These are different things: hudud were limited, needed very strict proof, and were meant to be avoided whenever there was doubt. They were never a license to beat suspects or extract information. See What are hudud punishments in Islam?

Sadly, some governments in Muslim-majority countries torture prisoners, just as some governments elsewhere do. That is a violation of Islam, not an example of it.