亦思马因，（？ - 1274年）元朝军人。回回人，西域旭烈（今阿富汗赫拉特）人。

善造回回炮，至元八年（1271年）应忽必烈所召，与阿老瓦丁至京师大都造新炮。1272年，献巨石炮，省力又射程远。1273年，随元军攻襄阳不克，亦思马因将重一百五十斤的回回炮置于城东南隅，发射，造成重大破坏，入地七尺。南宋安抚吕文焕因恐惧献城投降。亦思马因以功赐银二百五十两，命为回回炮手总管，佩虎符。1274年病故。儿子布伯世袭。

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Ismail (; 亦思马因|p= Yisimayin|w=I-ssŭ-ma-yin; died 1330) was a Muslim Iraqi counterweight mangonel expert who served the army of the Yuan dynasty in the conquest of the Southern Song dynasty.

In 1271, Kublai Khan dispatched envoys to obtain persons skilled in the management of mangonels trebuchets from his kinsman Abaqa, the Ilkhan in Persia. The latter sent Al al-Din and Ismail, together with their families, by post route to Hangzhou, where they began by building large mangonels which they erected in front of the city gates. In 1273 he served at the Siege of Xiangyang. He surveyed the approaches, and planted a mangonel at the southeast corner. Its weight was 150 catties (over ) and when the machinery was discharged, the noise was said to shake heaven and earth. It broke down all before it, and pierced the ground to a depth of .

Yisimayin died in 1330 and was succeeded by his son Yakoob.