The 24-hour walk-out by more than 850 Arriva Yorkshire bus drivers started at 3am, after members of the Unite union rejected a pay deal and voted for industrial action.
Arriva runs services across the region including Leeds, Wakefield, Pontefract, Castleford, Dewsbury, Batley, Heckmondwike and Morley.
The company said all Arriva services will cease from 6.30pm today, and only limited services will operate during the strike, with some bus times changed to hourly and certain areas not being served.
It comes after staff at Leeds bus firm First staged three 24-hour strikes in Leeds during the summer, which caused service disruption for commuters across the city.
Phil Bown, regional officer at the Unite union, said: “Strike action is not a step our members take lightly, but after nearly 12 months of circular talks they have become increasingly angry about being strung along by Arriva bosses."
Nigel Featham, regional managing director for Arriva Yorkshire and North East said “First and foremost we want to wholeheartedly apologise to our customers who will be affected by this industrial action."
The full list of service changes and disruption is available on Arriva Yorkshire’s www.arrivabus.co.uk/disruptions website.