Candlelight vigils will be held across the country on Friday to raise awareness of support available for those experiencing dark times over the Christmas period.
The Samaritans is organising vigils, walks and carol-singing events in a number of towns to coincide with the longest night of the year.
The charity has highlighted that its volunteers received 53,500 calls from people in need last December.
It has 1,300 volunteers on duty round the clock throughout the month this year.
Cindy O'Shea, Samaritans Irish regional director and a volunteer in the charity's Cork branch, said: "Christmas is a happy time for many, but for others it can be quite challenging. Bereavement, loneliness, relationship and family problems, depression, abuse and drug and alcohol misuse can feature heavily throughout the festive break.
"Being at the end of the phone to support someone during their darkest hours, especially over Christmas, is an incredible feeling. It's really important that people know someone is there for them if they are struggling through the day.
"Whether you're on your own, or alone in a crowd, feeling lonely and isolated can be exacerbated at this time of year.
"It's really important we highlight that whatever people are going through, at whatever time of the day or night, we're here to listen."
Teresa Bell, who has volunteered on Christmas Day for the past 19 years, said people's problems can crystallise over the festive period.
The Athlone branch volunteer said: "There's so much 'happy clappy' stuff for weeks in the run-up to Christmas, especially on television, and it can be difficult when it's not like that at home.
"People can be alone at Christmas, and sometimes that's by choice, but for others they may be bereaved, separated or have fallen out with family, and they find it difficult to get through the season. It's very special to be there for someone on Christmas Day."
Mary Deery will again volunteer in the Derry branch this Christmas.
"Until you've sat in a Samaritans phone room and taken those calls over Christmas, you have no idea how tough it can be for a lot of people," she said.
"Christmas feels like a condensed version of that, people's problems seem to be turned up a notch at this time of year, it can be tough, but it also makes it extremely rewarding.
"For me, not to be answering the phones over Christmas just isn't Christmas at all. The best present we can give someone is our time to listen."
For more information, [url=http://www.samaritans.org/christmas2018]click here