West Wales and the Valleys qualify for more than Â£2bn in EU aid between 2014 and 2020, due to low levels of wealth.
But the money - which has been paid ever since 2000 - will come to an end once the UK leaves the European Union.
The Conservatives' manifesto says the party aims to create a "Shared Prosperity Fund", with Welsh ministers to be consulted on the details.
The campaign document says the current EU scheme is "expensive to administer and poorly targeted", pledging its replacement will be "cheap to administer, low in bureaucracy and targeted where it is needed most".
The manifesto, published on Thursday, states: "We will use the structural fund money that comes back to the UK following Brexit to create a United Kingdom Shared Prosperity Fund, specifically designed to reduce inequalities between communities across our four nations.
"The money that is spent will help deliver sustainable, inclusive growth based on our modern industrial strategy."
Welsh Liberal Democrat leader Mark Williams said EU aid had been essential "in creating and safeguarding jobs, bringing our infrastructure into the 21st Century in many parts of the country, and providing opportunities for new entrepreneurs".
"Liberal Democrats would launch a Â£100bn package of additional infrastructure investment for the UK, to create jobs, build homes, and invest in the green economy to create an economy that works for everyone," he said.
Plaid Cymru has promised to demand that Wales continues to receive "every single penny" of the money it currently receives from the EU, once the UK leaves the bloc.
A new fund to replace EU economic aid will be created by the Conservatives if they win the general election.