The £1m give-away will appear on packs of Weetabix, Weetabix bitesize, Weetabix Minis, Oatibix, Ready Brek and Weetos.
The Lion Capital-owned breakfast cereal company will aim to attract new consumers to the brands and encourage continued purchases from existing consumers.
The promotion, which was created in partnership with Dialogue 141, will appear in store from the beginning of September.
To win, consumers will need to enter a code found on the inside of their pack on a specially created website. The site will take consumers on a virtual search for their cash around the UK.
There are almost 50,000 chances to win with the £1m prize pool ranging from £10 to £100,000.
Tony Corp, Weetabix marketing controller, says: “The ‘win £1m with Weetabix’ promotion is very exciting for the brand and is expected to create huge interest, driving consumer trial and boosting sales across all participating brands.”