Members of the union are currently in dispute over pay.
This morning the union confirmed drivers in both Ulsterbus and Metro bus have rejected the latest pay offer from management.
They described it as 'inadequate in the face of spiralling living costs'.
IN PICTURES: Unite strike action outside Strand Rd Council offices, Derry todayThe strike is likely to shut down all bus transport services for the duration.
General Secretary Sharon Graham of Unite said: “Unite bus drivers in Translink and Ulsterbus have increasing bills to pay like everyone else.
“The employers have to grasp that with inflation reaching levels unprecedented in a generation, these workers deserve pay that protects them from the living costs crisis and they have Unite’s full support as they take strike action.”
The strike action will involve members of both Unite the union and the GMB whose members also rejected the latest pay offer.
Unite deputy regional secretary Davy Thompson said: “This action is likely to shut down all bus services across Northern Ireland and will be hugely disruptive to public transport. Translink management still has the opportunity in coming days to avert this outcome by returning to the table and making an improved offer that meet the needs of Unite’s members.”