The company behind the Prize Bond weekly draw is introducing a once-a-year jackpot of €1m.
The draw for the new top prize will take place each December in the run-up to Christmas.
The Prize Bond Company is also increasing the currently monthly jackpot prize from €150,000 to €500,000 for the remaining 11 months of the year.
The first €500,000 draw takes place on Friday, to mark the 50th anniversary of the first draw in September 1957. There are close to 100 million prize bonds held, with a total value of around €590m.