Dozens of services have been cancelled today by Bus Éireann "due to operational issues".
The routes affected are predominantly in counties Galway, Mayo and Sligo. Some services between Dublin Airport and counties Waterford and Wexford have also been cancelled.
Intending passengers are asked to check the Bus Éireann twitter account for updates.
In a statement, the company apologised for any inconvenience caused and said it is actively recruiting for drivers throughout the country.
"Typically, service issues arise from a number of factors depending on location. This can include challenges in driver recruitment, driver unavailability often at short notice and more recently difficulty in hiring contractors to support services. This has more impact at comparatively smaller depots," the statement added.
"Where it is unfortunately necessary to cancel a service, we manage this to minimise the impact on customers, for example temporarily reducing frequency on higher frequency routes and making every effort to ensure the last service of the day operates."
