Scotland's last coal-fired power station, Longannet in Fife, is to close on 31 March next year.
Its owner, Scottish Power, said the high cost of connecting to the grid was to blame.
The company has also announced it is abandoning plans to build a new gas-fired power station at Cockenzie in East Lothian.
Longannet, which opened in 1972, is one of the biggest coal-fired power stations in Europe.
The power station employs more than 230 staff but Scottish Power said it hoped to avoid compulsory redundancies.
The news will leave Scotland heavily dependant on SSE's gas-fired power station at Peterhead and EDF's two ageing nuclear stations at Hunterston and Torness.
It is likely to lead to renewed debate about our growing reliance on renewables and generating capacity elsewhere in the UK.
Energy Minister Fergus Ewing said: "Scottish Power's decision to close Longannet in March 2016 is deeply regrettable and has far-reaching consequences for Scotland.
"This is a worrying time for Longannet workers and the Scottish government and its agencies will do everything possible to support the 230 directly employed staff who will be affected by this announcement."
Trade union Prospect said the news was a "body blow" to staff and the Fife economy.
Prospect negotiator Richard Hardy said it would also hit Scotland's hopes of remaining self-sufficient in energy generation.
He said: "It is extremely disappointing that, despite the efforts of Scottish Power and the Scottish government, it has not been possible to put in place ways of keeping Longannet open until its original planned closure date of 2020."
Neil Clitheroe, chief executive of retail and generation at Scottish Power, said it was "a sad day".
"We have explored every potential option to keep the station open, and we still maintain that Longannet could continue generation in to the next decade under the right economic conditions.
"Our main focus now is consulting with staff to ensure we find the best outcomes possible for all of the 236 impacted employees, many of whom have spent their entire career at the station.
"We would like to thank everyone at the station for their professionalism and continued commitment, and we know that the last few months have been very difficult."
Scottish Power said it still had major investment plans, with the company in the advanced stages of development for a new gas power station adjacent to its existing site at Damhead Creek in Kent and one of the largest offshore wind farms in the world off the coast of East Anglia.
A National Grid spokeswoman said: "The decision on the future of Longannet power station ultimately one for Scottish Power to make and is based on a range of commercial factors."
She added that a review of transmission charging for Scottish generators was coming into force next year, which would lead to "a significant reduction in charges".
A spokesperson for the UK's Department of Energy and Climate Change said: "This is obviously disappointing news for everyone connected with Longannet, but people in Scotland can be assured that energy security will be unaffected."
The DECC said that Scottish consumers had some of the lowest transmission charges in the UK because the costs were spread across the country.
Lang Banks, WWF Scotland director, said the closure announcement marks "an historic, but important step in Scotland's energy transition.
"While Longannet has served the nation for many years, it is Scotland's single biggest source of climate emissions and a combination of its age, air pollution rules, carbon pricing and transmission charging have made closure inevitable.
"The recent Scottish Parliament inquiry into energy security provided ample evidence from the National Grid and other experts that Scotland's electricity supply is absolutely secure without Longannet."
Lewis Macdonald, Labour's shadow energy minister, said: "Although this news will come as no surprise to Longannet employees, it is nevertheless deeply disappointing that Scottish Power has now confirmed the closure of the Fife power station up to four years earlier than previously anticipated.
"Over 200 job losses will hit the workers, their families and local communities hard, and it is vital that the Scottish government responds accordingly.
Murdo Fraser, Scottish Conservative energy spokesman, said: "While this news has come as no surprise it nevertheless represents a serious blow to the Fife and wider Scottish economy.
"The reality is that the pursuit of low carbon energy has meant that coal burning plants across the UK have no long-term future."