Transport and Garda chiefs have urged motorists to take extra care on the roads this Christmas Day.
A man was killed on the N11 in Wicklow after being hit by a car in the early hours of the morning between Newtown Mount Kennedy and Rathnew. He was walking near Coyne's Cross at about 1.20am when the accident happened.
Meanwhile, Bus Eireann was providing a special Christmas Day service between the country's main towns and cities to help thousands of stranded passengers get home.
Dublin Airport was closed for the day and is expected to reopen early on Sunday.
All main routes were open but the Road Safety Authority (RSA) warned that while the big freeze will begin to ease in the next 24 hours, driving conditions will remain treacherous.
RSA chief executive Noel Brett pleaded with road-users to take extreme care.
"There is a danger that road-users, and particularly motorists, will be lulled into a false sense of security as conditions improve after the recent freezing conditions," he said.
"Roads right across the country will remain extremely dangerous, with lingering patches of snow and ice posing serious risks for all road-users."
Met Eireann also warned of a risk of localised flooding as snow and ice begins to melt and rain moves in from the west and south.
There is also a danger of further snowfalls and freezing rain over the next 24 hours.