The man in his 60s was travelling with another cyclist when he was involved in a collision with a car near Holywood shortly before 6.30am.
Councillor Andrew Muir said: “It is heart breaking to hear of another death on our roads and I want to pass on my deepest condolences to the family and friends of the man who sadly lost his life today.
“This was a terrible tragedy and one that highlights that we all must be vigilant and exercise extreme care when using the roads, especially with an increased number of pedestrians and cyclists out enjoying the good weather.”