The Gregg River is a short river in west-central Alberta, Canada. The river is named after John James Gregg (1840–1941), a prospector and trapper prominent in the area.

The Gregg River forms at the confluence of a number of minor creeks near the Cardinal River Coal Mine, at the base of Mount Sir Harold Mitchell. The river then flows northwest, taking on a number of tributary creeks before joining the McLeod River, which in turn flows into the Athabasca River. The Gregg is bridged by Alberta Highway 40.

• Berry's Creek
• Sphinx Creek
• Drinnan Creek
• Warden Creek
• Teepee Creek
• Wigwam Creek

• List of Alberta rivers