"Thousands of workers at 18 bus companies in London are to stage a one-day strike on 13 January, the Unite union has announced.
The action is part of a long-running campaign for a single agreement covering their pay, terms and conditions.
There are more than 80 different pay rates in operation, said Unite.
Transport for London (TfL) said it was "very disappointed" Londoners would be disrupted.
Wayne King, Unite's London regional officer, said: "Strike action is not a step our members take lightly, but bus workers who keep London moving 24-hours a day, seven-days-a-week, have had enough of pay inequality and unfair pay disparities."
Mike Weston, TfL's director of buses, said: "Bus drivers are employed by private companies and their pay and conditions are a matter for those companies and the union to discuss.
"The current system provides the best value for money for the residents and visitors to London and allows the individual bus companies to determine the best terms and conditions for their individual operating requirements."
The bus companies involved in the dispute are: Arriva North, Arriva South, Selkent, London General, Metroline, Metroline West, Metrobus, CT Plus, London United, Abellio South, Abellio West, London Sovereign, Stagecoach, Blue Triangle, Northumberland Park, Tower Transit, Docklands and London Central."
Fonte BBC News