Anyone who thinks they may be descended from big names in Welsh history will be able to go online to use a genealogy project begun almost 80 years ago.
Owain Glyndwr began a failed revolt against English rule of Wales
The Welsh database from 300-1500AD is based on 26 volumes by Peter Bartrum, aged 99, who started it in 1929.
Family historians may be able to shed light on links to the likes of Llywelyn the Great or Owain Glyndwr.
Aberystwyth University is putting them online - but it will take three years to transfer to a computerised system.
However, once completed people will be able to trace an ancestral line by searching a name online.
Mr Bartrum, who is from London and has no family ties with Wales, handed his work over to the university recently.
Prof Gruffydd Aled Williams, head of the Welsh department, said Mr Bartrum's work "was an important source for academics and historians".
"It makes it possible to identify a person's lineage, his period and region with a minimum of effort, work which would otherwise take months of researching original manuscripts," he added.
"In theory, anyone who can trace their ancestry back to the 16th Century should be able to go back much further thanks to Dr Bartrum's work."
In 1974, Mr Bartrum published eight volumes called Welsh Genealogies AD 300 - 1400, and a further 18 volumes for 1400 - 1500 in 1983.
The university has received £300,000 from the Arts and Humanities Research Council to create the database.