The retailer praised Ahearne's "seven years of rigorous studying and hard work"
hail ing it
a "great accomplishment".
Ahearne, 46, previously worked for eight years as a winemaker in Australia, including stints at Charles Melton and Orlando Wyndham. She is the only MW in the M&S team.
Ahearne said: "Achieving the Master of Wine feels fantastic as it has been such a big part of my life for a long time. Working, studying and trying to have a life at the same has not always been very easy but it was worth it.
" This doesn't mean my education has come to an end, I will always continue to learn more about wine and find stunning new wines for our customers to enjoy."
Ahearne is among 15 new MWs announced by The Institute of Masters of Wine, including for the first time candidates from Spain and Brazil. The IMW said this year's passes demonstrated its "growing internationalisation", with candidates from the UK, US , Australia, Austria, Canada, France, Germany, Norway, Singapore, Sweden and Switzerland also obtaining the qualification.
The new MWs will be presented with their certificates at an awards ceremony on Nov 5 at Vintners' Hall in London.