Police cordoned off the area, closing the northbound carriageway of the motorway after the body was seen by a passing motorist at about 7am. The closure, which was still in place 12 hours later, caused traffic chaos.
Police were unable to indicate whether they believe the death is suspicious. But locals expressed shock after hearing the incident surrounded a young woman who had jumped from nearby Cambusbarron bridge.
Green barriers surrounded the area underneath the bridge where the body was found and a tent was put up within the exclusion zone, near Junction 9 Bannockburn Interchange. Drivers were advised to avoid the area if possible from 8.46am yesterday with Central Scotland Police warning of delays during the evening rush hour.
Seven hours later, police said the M9 was remaining close to allow investigation to continue and that the woman had not yet been identified.
Chief Inspector Gordon Dawson said: "We are keen to hear from anybody who was on the M9 between 06:15 and 07:00. We are particularly keen to hear from anybody who may have seen a young woman close to the motorway or on Birkhill Road bridge, in Cambusbarron, which crosses the motorway.
"The motorway is generally quiet at this time of the morning with commuter traffic but busier with heavy good vehicles and we are keen to hear from any driver or operator who had vehicles in the area around this time.
"I also thank motorists for their patience to allow the investigation to continue."
A contraflow system was put in place between Junction 9 Bannockburn Interchange and Junction 10 Craigforth.
Traffic Scotland subsequently reported long delays on the M80.