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.

Last week the IOC said individual sports' governing bodies must decide if Russian competitors are clean amid claims of state-sponsored doping.
But it now says the newly convened panel "will decide whether to accept or reject that final proposal".
More than 250 Russian athletes have so far been cleared to compete.
The three-person panel comprises Ugur Erdener, president of World Archery and head of the IOC medical and scientific commission, Claudia Bokel of the IOC athletes commission, and Spanish IOC member Juan Antonio Samaranch Jr, son of the ex-IOC president of the same name.
The World Anti-Doping Agency (Wada) had recommended all Russian athletes be banned after its independently commissioned report found evidence of a four-year "doping programme" across the "vast majority" of Olympic sports.
The IOC stopped short of applying a blanket ban in a move criticised by Wada and others, while swimmers Vladimir Morozov and Nikita Lobintsev have become the first Russian athletes to appeal against their ban to the Court of Arbitration for Sport.
The Olympics start in Rio on Friday.
Meanwhile, Russian whistleblower Yulia Stepanova has asked again for the IOC to reassess her exclusion from Rio.
The 800m runner's testimony helped shed light on the scale of doping in Russian sport, and she was to compete under a neutral flag in Rio.
But the IOC ruled that she should not be allowed to take part as she had previously failed a doping test.
In a letter to the IOC on Saturday, Stepanova and her husband Vitaly asked the body to "reassess the decision on Yulia".
The IOC responded by saying it had rejected any review of her case and had not discussed the matter at its executive board meeting.
"The final decision has been taken already," IOC spokesman Mark Adams said.
A new fund to replace EU economic aid will be created by the Conservatives if they win the general election.
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The International Olympic Committee (IOC) says a three-person panel will have the final say on which Russian athletes can compete at the Rio Games.