Abū Ibrāhīm Ismā'īl ibn Aḥmad (Persian: ابو ابراهیم اسماعیل بن احمد سامانی‎‎; May 849 – November 907), better simply known as Isma'il ibn Ahmad (اسماعیل بن احمد), and also known as Ismail Samani (اسماعیل سامانی), was the Samanid emir of Transoxiana (892–907) and Khorasan (900–907). His reign saw the emergence of the Samanids as a powerful force. He was the son of Ahmad ibn Asad and a descendant of Saman Khuda, the founder of the Samanid dynasty who renounced Zoroastrianism and embraced Islam.

Isma'il was born in Farghana in 849—he was the son of Ahmad ibn Asad, and had a brother named Nasr I, who ascended the Samanid throne in 864/5. During Nasr's reign, Isma'il was sent to take control of Bukhara, which had been devastated by looting on the part of forces from Khwarezm. The citizens of the city welcomed Isma'il, seeing him as someone who could bring stability.

Soon afterwards, a disagreement over where tax money should be distributed caused a falling out between Nasr and Isma'il. A struggle ensued, in which Isma'il proved victorious. Although he took effective control of the state, he did not formally overthrow his brother, instead remaining in Bukhara. He did so because Nasr had been the one whom the Caliph had given the formal investiture of Transoxiana to; in the caliph's eyes, Nasr was the only legitimimate ruler of the region. Furthermore, the Saffarids of Sistan had claims on Transoxiana; the overthrow of Nasr would have given the Saffarids a pretext for invading. Isma'il therefore continued to formally recognize Nasr as ruler until the latter's death in August 892, at which point he officially took power.

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