ʿIlm al-Kalām (Arabic: عِلْم الكَلام, literally "science of discourse"), usually foreshortened to Kalām and sometimes called "Islamic scholastic theology" or "speculative theology", is the philosophical study of Islamic doctrine ('aqa'id). It was born out of the need to establish and defend the tenets of the Islamic faith against the philosophical doubters. However, this picture has been increasingly questioned by scholarship that attempts to show that kalām was in fact a demonstrative rather than a dialectical science and was always intellectually creative.

The Arabic term Kalām means "speech, word, utterance" among other things. There are many possible interpretations as to why this discipline was originally called so; one is that one of the widest controversies in this discipline, in the second and third centuries of Hijra, has been about whether the "Word of God" (Kalām Allāh), as revealed in the Quran, is an eternal attribute of God and therefore not created, or whether it is created words in the sense of ink and sounds. A scholar of Kalām is referred to as a mutakallim (plural: mutakallimūn), and it is a role distinguished from those of Islamic philosophers, jurists, and scientists.