The two carriers are expected to be ready from 2014-16
A major contract has been awarded to modify a dry dock in preparation for work starting on two aircraft carriers.
Babcock Marine in Rosyth, Fife, which is hoping to secure a deal to build the ships, has awarded the £35m contact to construction firm Edmund Nuttall.
Defence Secretary Des Brown has described the contract as a major milestone for the shipbuilding project.
The 65,000 tonne ships should be assembled at the yard and are expected to be ready from 2014-16.
Overall, the contract to build HMS Queen Elizabeth and HMS Prince of Wales is worth £3.8bn.
They will be the largest ships ever built for the Royal Navy.
Babcock, which is part of the UK Aircraft Carrier Alliance, secured the deal in July 2007.
A total of £50m will be invested at the Rosyth site, including the installation of the biggest crane in the UK.
Des Browne said: "This programme will bring real benefits to Fife and Scotland."
The news has been welcomed by the Mid-Scotland and Fife MSP, John Park.
He said: "Make no mistake, it's the skills dedication of the workforce at Rosyth that has given the dockyard a future to look forward to.
"It's not always been easy but when we see developments like the construction of the new dock it reminds people that the fight to keep the yard afloat over the last 20 years was worth it."
Chief Executive of Edmund Nuttall, Martin Rogers, said: "We are understandably delighted to have secured this major package of work.
"We are looking forward now to starting work on site."