The government wants to train a million people in England by 2015 to become "dementia friends", able to spot signs of the illness and help sufferers.
It is part of plans to raise awareness of the condition, which affects nearly 700,000 people in England.
Prime Minister David Cameron has said dementia is a national crisis and awareness of it is "shockingly low".
The number of people with dementia is expected to double in the next 30 years because more people are living longer.
The government is launching the Dementia Friends scheme, which has been adapted from a similar programme in Japan that recruited three million volunteers.
Sessions in workplaces and town halls across the country will explain what dementia is, what it is like to have the condition and what people can do to help if they meet someone with the symptoms.
It is hoped that charities, businesses and the wider public will get involved.
The prime minister said: "We cannot underestimate the challenge we face in dealing with dementia in our country."
He has already promised to double the research budget for the disease to £66m by 2015.
"There are already nearly 700,000 sufferers in England alone, but less than half are diagnosed and general awareness about the condition is shockingly low.
"Through the Dementia Friends project we will for the first time make sure a million people know how to spot those tell-tale signs and provide support.
Jeremy Hunt, the Health Secretary, said he wanted the country to be "one of the best" places for dementia care in Europe.
He said: "Too many people with dementia feel cut off, lonely and fearful without the support and understanding they need."
"People with dementia and their carers should never feel barred from everyday activities like shopping for groceries or spending time with friends.
"We are putting in place plans to make next year a year of raising awareness of dementia."
Dementia Friends will be given a forget-me-not badge. The scheme will cost £2.4m.
The chief executive of the Alzheimer's Society, Jeremy Hughes, said: "We want to rally a million people behind the cause of helping make a better life for people with dementia.
"I am confident we will not only meet this target but beat it. Dementia is everyone's problem and we all need to be part of the solution."
Dr Eric Karran, director of research at Alzheimer's Research UK, said: "At a cost of £23bn a year to the UK economy, we all agree that dementia is not a problem we can ignore. Finding treatments for Alzheimer's and other dementias is no easy task, but it's one we must tackle if we are to make a real difference to people's lives."