Council and school support staff are to strike on July 10 after voting in favour of industrial action over pay.
Unison said its members in England, Wales and Northern Ireland will walk out for 24 hours, with other unions set to announce a similar move in the coming week.
Unison announced that its local government members backed action by 58% in protest at a pay offer worth 1% for most workers.
General secretary Dave Prentis, said: "We have a clear majority for strike action so a one day strike will go ahead on July 10. We expect to be joined in that action by other unions in local government and will be campaigning amongst our members for maximum support on that day.
"Many of our members are low paid women earning barely above the minimum wage, who care for our children, our elderly and our vulnerable and they deserve better treatment than they have had at the hands of this government. The employers must get back into talks immediately to avoid a damaging dispute."
Unison said local government workers have been "condemned" to three consecutive years of pay freezes, followed by below-inflation rises in 2013 and 2014, leaving their pay reduced by almost 20% since the coalition came to power.
The GMB and Unite will announce voting results over the next week, while t he Public and Commercial Services union is also balloting its members for a strike in a long-running dispute over cuts in the civil service, with the result also due by the end of the month.
Mr Prentis has predicted that a walkout on July 10 could be bigger than the General Strike.
Members of the National Union of Teachers will also take industrial action on July 10, while firefighters in England and Wales have staged a series of walkouts over pensions over the past year and have not ruled out further stoppages.
Meanwhile, midwives in England could soon be balloted for industrial action in protest at the Government's controversial decision not to accept a recommended 1% across the board pay rise for NHS staff.
Thousands of midwives and maternity support staff are currently being consulted on whether they want a formal ballot for action.
Jon Skewes, director of policy and employment relations at the Royal College of Midwives, said: "Midwives are really angry that the Government said to them they'd get a 1% pay rise but now only staff at the top of their pay scales will get that rise, and it's not consolidated into their pay.
"Jeremy Hunt (the Health Secretary) has picked out health workers for harsher treatment on pay than anyone else in the public sector.
"This is the time for midwives to take a stand because the Government is intent on assaulting their pay and conditions."
Other health unions are warning of ballots for industrial action, which could see a second wave of public sector strikes in in the autumn.
Voting in Unison's ballot was 49,836 (58.7%) in favour, and 35,062 (41.3%) against.
A Local Government Association spokesman said: "It is disappointing that Unison will be proceeding with strike action. Local government staff have worked wonders while councils have been tackling the biggest funding cuts in living memory and we have no doubt that many will still be at work on the day of strike action.
"The pay offer we have made would increase the pay of most employees by 1% while the lowest paid would receive an increase of more than 4%. This is the fairest possible deal for our employees given the limits of what we can afford.
"This strike will not change the pay offer we have made, but it will mean those who take part lose a day's pay."
Civil servants in the Ministry of Justice (MoJ) and tax workers are to take industrial action in the coming days in separate disputes over jobs and privatisation.
The Public and Commercial Services union said tens of thousands of HM Revenue and Customs staff across the UK will hold rolling strikes this week, including in Scotland and the North East today, Yorkshire and Humberside and Eastern England tomorrow, London, the South East and South West on Wednesday, Midlands and Northern Ireland on Thursday and North West England and Wales on Friday.
General secretary Mark Serwotka said: "HMRC plays an essential role in our economy and our society, collecting the taxes that fund the other public services we all rely on. But it is being systematically undermined by unnecessary and politically-motivated cuts."
PCS members at the MoJ in Newport, South Wales and Bootle on Merseyside will strike next Monday in a row over privatisation.
Mick Cash, acting general secretary of the Rail, Maritime and Transport union, warned of a strike ballot among Network Rail workers in a row over spending cuts.
He told the union's annual conference in Bristol: " We are talking about a ballot across the whole of Network Rail if cuts aren't stopped, a ballot that would include signallers, operations and the maintenance works on the infrastructure.
"We are being driven down that road by cash-led cuts, imposed by the Government, which threaten life and limb at a time of surging rail demand and while the private train companies are robbing the railways blind.
"RMT members have had enough of being kicked about and the Government and Network Rail need to wake up to a few home truths. Our railways stand on the brink, and while George Osborne is posturing for the cameras for publicity stunts about developments years off into the future, in the here and now our railway is edging closer and closer to disaster."