Six senior managers and two companies have been charged over the Hatfield rail crash, which killed four people and injured dozens more in October 2000.
Four people died in the crash
Network Rail, Balfour Beatty and the managers have been charged with gross negligence, manslaughter and an offence under the Health and Safety at Work Act.
If found guilty, the individuals could face life imprisonment and the two firms could receive an unlimited fine.
Both companies have said they will defend themselves and their employees against the charges.
A further six men are being summonsed for offences under the Health and Safety at Work Act only, including former Railtrack boss Gerald Corbett, who is now chairman of Woolworths.
The crash in Hertfordshire happened when a broken rail caused a GNER East Coast high-speed train to derail just south of Hatfield station.
THE SIX INDIVIDUALS CHARGED
Charles Pollard - Railtrack
Alistair Cook - Railtrack
Sean Fugill - Railtrack
Keith Lea - Railtrack
Nicholas Jeffries - Balfour Beatty
Anthony Walker - Balfour Beatty
Railtrack, which has since been taken over by Network Rail, was in charge of the rail infrastructure at the time of the crash.
The stretch of line where the crash happened was managed by Balfour Beatty.
The six who have been charged have been bailed to appear at Central Hertfordshire Magistrates' Court in St Albans on 14 July.
The two corporations, and the six who received summonses, are due to appear at the same court on the same date.
This is not the first time a company has been prosecuted for manslaughter, but no major company has ever been found guilty.
However, the lawyer for the relatives of those who died in the crash welcomed the news.
"We are pleased that steps are now being taken to bring this matter to the courts," said solicitor John Pickering.
"My clients... are concerned that those responsible should be held to account."
In a statement Network Rail said both the company and its employees fully intend to defend themselves against the charges.
"As the company stated last week, we believe that our employees conduct their duties to the best of their abilities with the sole intention of delivering a safe, reliable and efficient railway network."
Its chief executive John Armitt said employees who have been charged would remain in their jobs pending trial.
"They have not been found guilty of anything and we believe it is appropriate for them to continue in their duties," he said.
Balfour Beatty said it saw no justification for the manslaughter charges.
"The charge of manslaughter against our maintenance business will be firmly defended as we see no plausible basis for it in law or on the evidence," it said in a statement.
"The individuals charged will have the company's fullest support in their defence of the charges against them."
Mr Corbett told BBC Radio 4's The World At One that he would also defend himself vigorously.
"I was the chief executive when something went wrong and that is why I immediately tendered my resignation," he said.
"But taking responsibility for one's organisation does not necessarily mean that I accept that the rail breaking was in any sense attributable to neglect on my part."
The biggest rail union, the RMT, said the decision to prosecute was right.
Crown Prosecutor Andrew Faiers said the decision to press charges was based on "substantial evidence".
The BBC's Business correspondent Russel Hayes said the corporate manslaughter charges had sent "seismic shockwaves" through Balfour Beatty and Network Rail.
"It is going to be an immensely complex case; there is a lot of evidence and it will certainly not be resolved quickly," he said.
Mr Hayes added that it was a "very aggressive" action on the part of the CPS to "try to bring these companies to justice for this accident".