Diageo has worked with the Irwin's baking group to develop the bread, which has now been launched in more than 250 stores of supermarket giant Tesco, across Ireland and the UK.
The move is a tentative first step for Diageo, already the world's largest alcoholic drinks group, into the retail food market.
Sales of Guinness have slipped in Ireland over the last couple of years, despite being brewed in the country since 1759 and retaining its image today as the nation's signature drink.
"We have been keen for some time to harness the qualities and taste of Guinness into suitable food products for the commercial retail market," said David Berry, licencing director of Diageo Europe.
"It's appropriate now to 'toast' the success of Guinness Whole Grain Bread, which we hope will pave the way for further mass market food product development for us."
The loaf is a wheaten bread containing 17 per cent Guinness, although the alcohol content evaporates during baking, Michael Murphy, business development manager at Irwin's, told BeverageDaily sister site BakeryAndSnacks.com.
"Guinness is such a strong flavour - you either love it or hate it but we've sampled it at shows in Dublin and the response was very positive." Irwin's predicted particularly strong sales for St Patrick's Day celebrations.
The bread is the latest in a string of Guinness innovations from Diageo Ireland, which have included both red and low alcohol versions of the drink.
The firm sold eight per cent less Guinness in Ireland in the year up to 30 June 2006, compared to the year before. Sales were also down three per cent in Britain.
The drink has been a victim of the Irish government's drive to curb excessive drinking in the country - Irish consumers are the biggest drinkers in Europe - and also of competition from other drinks brands, such as Magners cider.