He has been named locally as Ronan Wilson from the Cookstown area.
Irish police said emergency services were called to Bundoran at around 9.20pm on Saturday after a pedestrian was “struck by a vehicle” on Atlantic Way.
“The pedestrian, a boy aged nine years, was pronounced deceased at the scene a short time later,” they said.
“The vehicle involved in the collision failed to remain at the scene.”
Gardai are appealing for witnesses and are particularly calling on the driver of the vehicle to come forward.
“Investigating Gardai are also appealing to those with video footage, including dash cam recordings, from Atlantic Way and Sea Road, and the general area at the time, to make it available to them,” they said.
Anyone with information is asked to contact Ballyshannon garda station on 074 9858530 or the garda confidential line on 1800 666 111.
His death was one of three on Irish roads over the weekend.
In Co Kerry, another pedestrian, a man aged in his 20s, was pronounced dead at the scene following a collision involving a taxi.
Emergency services were alerted shortly after 2am to the incident on the R553 at Ballydonohoe, Lisselton, near Ballybunion.
"The pedestrian, a male in his 20s, was pronounced deceased at the scene a short time later," Gardai said.
"His body has since been removed to the mortuary at University Hospital Kerry. The driver, a male in his 40s, did not require immediate medical treatment."
Meanwhile, a motorcyclist died following a road collision involving a pedestrian in Dublin at about 2.45am on Sunday.
The motorcyclist, a man in his early 20s, was pronounced dead at the scene at a roundabout on Whitestown Way in Tallaght.
The pedestrian, also a male in his 20s, was taken by ambulance to Tallaght Hospital, where his injures are not believed to be life-threatening.
Gardai are appealing to anyone with information or who may have witnessed any of these crashes to contact them.