They are among 35 rescuers to be awarded for saving 22 people from drowning in Ireland this year.
They will be presented with their Seiko Just In Time Rescue Awards by Environment Minister Alan Kelly in Dublin Castle this afternoon.
The gardai are Trevor Keating, Shaun Sweeney and Grainne McLoone who rescued a 12-year-old Downs Syndrome lad whose father became concerned when he swam out too far at Neds Point, Buncrana, on September 18.
When the gardai attempted to have the boy swim back he misunderstood and thought it was a game.
Gardai Sweeney and McLoone kept the boy occupied while Garda Keating entered the water, swam to him, reassured him and brought him to safety.
The 21-year-old Donegal-based civilian who will received a similar award this afternoon is Shaun Haughey from Drumkeen, near Letterkenny, who works for hospital equipment maker Medizise..
On August 24 at Rathmullen Pier, Shaun heard screams from where four people had jumped into the water. Only two had made it safely back to the steps of the pier.
Shaun, who was fishing, reacted quickly, removing some of his clothing and entered the water. He took hold of a ringbuoy that one of the others had previously thrown and swam towards the now hysterical casualties. He managed to calm the distressed swimmers, support them with the ringbuoy and swim towards the pier steps where another man helped all three to exit the water.