Motorists are being advised to expect delays this morning, as the sixth annual Electric Picnic Festival gets underway in Stradbally in Co. Laois.
Around 30,000 people are expected to attend.
There are a number of public transport options, with buses running from various locations around the country, and a shuttle bus will also run from Portlaoise train station to the festival site.
Organiser John Reynolds said he always tries to ensure the festival accommodates a wide range of music tastes.
Brian Wilson, the Flaming Lips, and Fleet Foxes are among those on this year's line-up.