Big Sandy Creek () is a tributary of the Milk River, approximately 50 miles (80 kilometers) long, in northwestern Montana in the United States.
It rises in the southern Rocky Boys Indian Reservation in the Bears Paw Mountains and flows southwest, then north past Box Elder, then northeast, joined by Sage Creek, and joins the Milk approximately 10 mi (16 km) west of Havre.
Big Sandy Creek has also been known as: Ahmi-Saptsiko, Sand Creek, and Un-es-putcha-eka.