3,000 poor and homeless people will be fed from the RDS today - more than double the demand just four years ago.
The Order of the Knights of St Columbanus offers a three course Christmas meal, with free buses running from the Mansion House, Clery's and the Four Courts.
It has been a festive tradition for nearly 100 years.
There are 500 sit down dinners this year, and 2,500 take away meals - that is two and a half times the demand just four years ago.
One of the volunteers, Katie Hogan, says it is a really special day at the RDS.
She says it is a 'bittersweet' day - while she will "never get used" to the increase in numbers attending the dinner, she adds that it is fantastic to see the number of volunteers also growing every year.
Many other charities and organisations around the country - such as Vincent de Paul, ALONE and Simon - will also be helping distribute Christmas meals today to those in need.
Any surplus food from the RDS dinner will be delivered to Brother Kevin's Capuchin Day Centre for the homeless.
Brother Kevin says he is expecting to be busy today, and his centre is expected to feed around 700 to 800 people:
