The supermarkets have all reduced its salted and unsalted butter prices from £1.99 to £1.89 for 250g packets.
Wholesale food prices have been falling globally, but UK food inflation is at its highest for 45 years.
The move comes after criticism supermarkets are not passing on wholesale price falls quickly enough.
Inflation was expected to fall below 10% last month, but soaring food prices meant it fell by less than expected.
Last month the Office for National Statistics - which measures the rate of prices increases - told the BBC you would expect to see global food price falls reflected in supermarkets "but we're not there yet".
And in March, the union Unite accused some retailers of "fuelling inflation by excessive profiteering".
In April industry body the British Retail Consortium said there is a three to nine-month lag to see wholesale price falls reflected in shops, and promised prices would come down over the next few months.
Asda and Morrisons have been approached for comment.
Sainsbury's said it was cutting the price of its some of its own-brand bread to 75p from 85p.
The supermarket said it was able to lower some of its bread and butter prices due to wholesale prices beginning to fall.
"Whenever we are paying less for the products we buy from our suppliers, we will pass those savings on to customers," the UK's second-largest supermarket chain said.
Aldi said it was cutting some bread to 75p from 79p, while Tesco cut some its own-brand bread from 85p to 75p.
Lidl said it had dropped the price of some butter to £1.89, and some bread to 75p, adding that it has a loaf priced at 39p.
The war in Ukraine has driven up food prices around the world, but the UK has also faced its own problems too - from Brexit red tape to labour shortages.
However, as commodity prices have started to fall, supermarkets have started to cut prices on some products - but not others.
Some of the earliest price falls have been in milk, with Aldi, Lidl and Asda recently following Sainsbury's and Tesco in cutting the price of milk by at least 5p.
* Keep track of what you have
* Head for the reduced section first
* Make better use of your freezer
* Make food last longer by understanding packaging
* Make use of local experts
Last summer, butter brand Lurpak said it had put prices up so dairy farmers would get a fair deal.
Some shoppers had expressed shock at rapidly rising prices, with a 750g tub of Lurpak priced at £7.25 in Sainsbury's in July 2022.
Farmers have been under pressure as milk prices have dropped, with one dairy farmer in Shropshire recently saying he is on a "knife-edge".
Sainsbury's said its price drop would not have an impact on how much it paid farmers.