The promotion covers the vast majority of public transport journeys
Children can travel free on all public transport services covered by the Leap Card for two weeks from Monday.
Free travel will automatically apply to any holder of a Child Leap Card when the card is presented.
The promotion covers the vast majority of public transport journeys - including Dublin Bus (excluding Airlink), Luas, DART services, commuter rail services in Dublin's "Short Hop Zone" and Bus Éireann services where Leap Card Validators are available.
Anne Graham, CEO of the National Transport Authority says: "Of course, this promotion doesn't just apply to Dublin. The historic cities of Cork, Galway, Limerick and Waterford are also included.
"At a time when a lot of people still find themselves under financial pressure, we want to do everything we can to make it easier for families to get out and enjoy all there is on offer throughout the network of public transport services covered by Leap.
"One way we can do this is by making sure that the cost of transport for families is not prohibitive and our Kids Go Free promotion does precisely that.
"It also gives that extra bit of freedom to the teenagers who can now meet up with their friends in town without breaking the bank and just as important, gets them into the habit of using public transport."
This offer is valid for Child Leap Card 4-15 and Child Leap Card 16-18, which is valid up to the holder's 19th birthday, as long as the card has at least 1 cent credit.
The NTA says it hopes the promotion will encourage families, children and teens to use public transport for their leisure activities in the school holidays, and to get out and about and enjoy more of what Ireland has to offer.