Just 0.1% in market share separates the top three grocery retailers, as competition in the sector intensifies ahead of the festive period.
Latest figures from Kantar Worldpanel for the 12 weeks to 8 October show SuperValu and Tesco both have a market share of 22%, with Dunnes Stores just behind on 21.9%.
Tesco has seen strong sales growth of 4.2% in the last year, helping to improve its market share by 0.4%.
SuperValu has also seen an increase in sales, up 0.5%, putting the two stores' market shares on a level footing.
With regard to the low-cost retailers, Lidl and Aldi both increased sales year on year - up 3.0% and 2.8% respectively.
Lidl's market share increased to 11.7%, while Aldi's rose by 0.1% to 11.6%.
Commenting on the figures, Director of Kantar Worldpanel David Berry said: "With Dunnes Stores only 0.1% behind SuperValu and Tesco, the top three Irish supermarkets are all fighting for the top spot.
"With the festive period just around the corner – the time of year when sales spike and shoppers aren't afraid to spend that little bit extra – the competition shows no signs of abating."
Mr Berry added: "With the recent trend towards own-label items, there's now some good news on the horizon for brands.
"This time last year sales of branded items dropped by 0.5% compared to the year before, however we're now seeing a return to form - with sales up 1.3%.
"At Christmas, shoppers tend to flock back to brands – partly for sentimental reasons and also as people are tempted to trade up at this time of year – so with the countdown to the festive season now well and truly underway, it's likely we'll see this trend continue into the New Year."