The price of standard domestic and international stamps is set to increase from next month.
A standard domestic stamp will increase from €1 to €1.10 from 19th March, while the price of an international stamp will also increase by 10 cent to €1.80.
It will be the first price increase since April 2017, with An Post saying it "reflects other European postal services’ price increases over the past three years".
In a statement, An Post said: "Increases in letter prices across Europe reflect the steady decline in traditional letter volumes globally due to e-substitution.
"An Post has invested to ensure that Ireland has one of the best postal systems in the world as it transforms from the old world of traditional letters to the new world of ecommerce parcels."
The postal service added that all existing purchased stamps will remain fully valid after the price increases come into effect, and that 10 cent stamps can be purchased to make up any difference in postage costs.
An Post says its efforts to invest in parcel delivery services are also continuing.
The firm is working towards a 'fully-automated sorting facility' for small packages at its mails centre in Clondalkin, with the site set to process around 70,000 parcels per day.