Qadi (also known as qaadi, qaadee, qazi, kazi or kadi) (Arabic: قاضي‎ qāḍī) is a judge ruling in accordance with Islamic religious law (sharia) appointed by the ruler of a Muslim country. Because Islam makes no distinction between religious and secular domains, qadis traditionally have jurisdiction over all legal matters involving Muslims. The judgment of a qadi must be based on ijmah, the prevailing consensus of the Islamic scholars (ulema).

The origin of the institution of qadi is the old Arab arbitrator, the Hakam, but qualities from officials in areas conquered by Arabs have been added to the structure.

The term "qadi" was in use right from the time of the Prophet Muhammad, and remained the term used for judges throughout Islamic history and the period of the caliphates. While the muftis and fuqaha played the role in elucidation of the principles of jurisprudence and the laws, the qadi remained the key person ensuring the establishment of justice on the basis of these very laws and rules. Thus, the qadi was chosen from amongst those who had mastered the sciences of jurisprudence and law.