Ishma-Dagan (𒅖𒈣𒀭𒁕𒃶, Ish-ma-da-gan, c. 2190-2146 BCE) was a ruler of the city of Mari, one of the military governors known as Shakkanakku in northern Mesopotamia, in the later period of the Akkadian Empire.
According to the dynastic lists, he ruled for 45 years, after Shu-Dagan, and was the third Shakkanakku ruler.
Ishma-Dagan was probably contemporary with the Akkadian Empire ruler Shar-Kali-Sharri.
He had two sons who succeeded him in turn as Shakkanakkus of Mari: Nûr-Mêr and Ishtup-Ilum.

He is also known from inscriptions by his son Ishtup-Ilum mentioning his father, in dedication tablets for the building of a temple: 
"Ishtup-Ilum, Shakkanakku of Mari, son of Ishma-Dagan, Shakkanakku of Mari, built the Temple for the "King of the country"
— Dedication tablet of Ishtup-Ilum.
Ishma-Dagan (𒅖𒈣𒀭𒁕𒃶, Ish-ma-da-gan, c. 2190-2146 BCE) was a ruler of the city of Mari, one of the military governors known as Shakkanakku in northern Mesopotamia, in the later period of the Akkadian Empire. According to the dynastic lists, he ruled for 45 years, after Shu-Dagan, and was the third Shakkanakku ruler. Ishma-Dagan was probably contemporary with the Akkadian Empire ruler Shar-Kali-Sharri. He had two sons who succeeded him in turn as Shakkanakkus of Mari: Nûr-Mêr and Ishtup-Ilum.
He is also known from inscriptions by his son Ishtup-Ilum mentioning his father, in dedication tablets for the building of a temple: 
"Ishtup-Ilum, Shakkanakku of Mari, son of Ishma-Dagan, Shakkanakku of Mari, built the Temple for the "King of the country"
— Dedication tablet of Ishtup-Ilum.
Ishma-Dagan