Factories in south Wales and Lancashire have started making "high quality" face coverings as part of a push to produce a million a week.
Some £14m is being invested by the UK government, with productions underway in Port Talbot and Blackburn.
Face coverings are already compulsory in shops across Scotland, and will be in England from 24 July.
Masks are also compulsory on all public transport across the UK, including Wales from 27 July.
"This is a major step to ensure that this country can meet any increase in demand for face coverings by working with British firms to establish the capability, capacity and skills required to manufacture these items at scale," said Cabinet Office Minister Michael Gove.
"These production lines will be able to get millions of face coverings to the public, without putting any additional pressure on NHS supply chains."