McCartney Creek is a 2nd order tributary to North Fork Flatwillow Creek in Fergus County. The creek originates on the east end of the Big Snowy Mountains and flows through a steep timbered drainage for 8 miles to its confluence with the North Fork of Flatwillow Creek. The creek is fed by four 1st order tributaries and gains substantial water from springs located throughout the upper reaches of the drainage. The major land use in the drainage is livestock range, other uses include timber harvest and recreation.