Staff will protest outside Swansea College from noon to 1300 GMT
Staff and students at three colleges in Swansea and Carmarthenshire are to protest over cuts in funding to sixth forms and further education in Wales.
They warn it will will lead to hundreds of redundancies and seriously hamper the recovery of the Welsh economy.
Protests are planned at Gorseinon and Swansea Colleges and at all five sites run by Coleg Sir Gar.
The assembly government said colleges had seen a small cut but £32.5m extra was being spent on 14-19 education.
Staff at Neath Port Talbot College walked out earlier this month over a £1.6m cut to the budget there.
Coleg Sir Gar staff say their college's budget has been cut by £1.2m with 89 posts under threat.
Steve Kelshaw of the Association of College Managers (ACM) at Coleg Sir Gar said: "I have been in further education for over 20 years and I have never seen a campaign launched by staff and students take off so quickly.
"Everyone concerned is dismayed at the scale of the cuts and we are struggling to understand why this is happening when we should be putting on more courses to help people through the recession - not adding numbers to the dole queue".
Dr David Hunt, chairman of Association of Teachers and Lecturers (ATL) at Swansea College, said a cut of over £1m would lead to the loss of popular courses for hundreds of students there.
"At best we think that the assembly government has simply not realised the impact of its cuts and should think again," he said.
Members of the University and College Union (UCU) and public sector union Unison, which includes technical, kitchen and ground staff, will also take part.
The unions want the assembly government to follow a recent UK government initiative which saw the skills secretary John Denham announce £500m for colleges to help people affected by the economic downturn retrain.
A Welsh Assembly Government spokesperson said: "The funding position is that schools have seen a small increase and colleges have experienced a 1% reduction in funding.
"We are facing tough economic times and a difficult budget settlement has meant having to make difficult choices.
"Government officials have, and continue to work closely with post-16 learning, to ensure that every assistance will be given through this difficult settlement.
"We are making a considerable investment in the implementation of 14-19 Learning Pathways by making available an additional £32.5m per annum to support 14-19 Networks to implement Learning Pathways.
"This funding is additional to monies already being provided to local authorities and further education institutions for 14-19 provision in Wales."