Dublin-born Galen Weston Jr, 45, now heads up the Canadian family empire, which was founded in 1882 by his great-grandfather.
Despite claiming the top spot for 2018, the Weston's family fortune fell €933million to €11.42billion (£10.05bn).
The rich list surveys the wealth of the 300 richest individuals and families in Ireland in a range of areas including entertainment, sport, business, technology and construction.
Denis O'Brien, businessman and the founder of Digicel, is in second place, with his fortune decreasing by €900million in the past year.
Third spot goes to Campbell's Soup heir John Dorrance whose wealth is up €100million at €2.6billion.
Earlier this week it was revealed that U2 had topped the entertainment list for a second-year running, with a combined wealth of €647million.
Former One Direction member turned solo artist, Niall Horan is the only person under the age of 40 on the list.
He has seen his wealth rise by €8million in the last year, largely thanks to a successful debut solo album.
Television producers Mark Burnett and Roma Downey have come in second place on the list with a shared wealth of €443million.
The man with the quick feet, Michael Flatley, sits in third place with earnings of €230million.
Ireland’s wealthiest actor Liam Neeson has €113million to his name, followed by peers Pierce Brosnan with €72million and Daniel Day-Lewis with €56million.