İslâm III Giray (Crimean Tatar: اسلام كرای ثالث, romanized: İslâm Gäray-i S̱âlis̱; 1604 – 10 July 1654) was khan of the Crimean Khanate for ten years (1644–1654), interrupting the reign of his brother Mehmed IV Giray. He was khan during the Khmelnytsky uprising of the Cossacks against Poland.

He was one of the many sons of khan Selyamet I (1608–10), three of whom were khans and four of whom were fathers of khans. See Selâmet I Giray#His sons. He was preceded and followed by his younger brother Mehmed IV. None of his sons were khans. Subsequent khans were mostly descended from his brother Bahadir.

During the second reign of Canibek Giray (1628–1635) he was a captive in Poland circa 1629–1632 ^[1] Under Bahadır I Giray (1637–41) he served as kalga. In 1637 or 1638 he led the Budjak Horde back to Crimea. In the winter of 1639–40 he captured 8000 Ukrainian slaves for the Turkish galleys. In 1641 Bahadir was followed by his and İslâm's brother Mehmed IV even though İslâm was older. İslâm went to Turkey and settled at a place called Sultania on the western side of the Dardanelles.

In 1644 the Ottoman Sultan dismissed İslâm's brother Mehmed IV and placed İslâm on the throne. İslâm appointed his younger brother Kyrym as kalga. As nureddin he continued Gazi, the son of his brother Mubarak. In 1651 Kyrym was killed at the Battle of Berestechko and was replaced by Gazi, the new nureddin being İslâm's younger brother Adil. Kyrym, Mubarak and Adil were all fathers of khans. İslâm is remembered as a builder and successful administrator. He tended to appoint non-nobles without antagonizing the clan leaders. For the Ukrainian rebellion see below. In 1654 he died of natural causes.