The price of a national stamp is going up from next month.
It will increase by 5c to €1.40, while rates for large envelopes and Registered Post will also go up on February 1st.
An Post has said it is seeing increasing transport, fuel and energy costs.
The company said the changes "will ensure the continuity of national letter services based on customers paying the same price for delivery of letters nationwide, regardless of distance."
The price of 10-stamp booklets will be €13.50 (€1.35 per stamp), while a box of 100 stamps will work out at €1.30 per stamp (a 10c reduction per stamp).
An Post Commerce Managing Director Garrett Bridgeman said Irish postage rates are still competitive.
"We have made every effort to minimise the necessary price increases by spreading them across letter products and services while ensuring top quality, sustainable services for all customers, wherever they live," he said.
"An Post’s quality of service is amongst the highest in Europe while our prices remain well below the average tariff.
"For the first time ever, our comparable domestic tariffs are below those of the United Kingdom.
"These increases are necessary to cover rising costs and ensure service continuity and innovation on par with the best in Europe.
"We're alleviating the impact on SMEs and personal customers by providing discounts and regular price promotions through the year at post offices and online," he added.
All existing stamps with ‘N’ (National) and ‘W’ (Worldwide) or specific euro denominations remain valid and fully useable after February 1st.
There will also be no increase in the International Letter stamp (€2.20) or the Digital Stamp (€2.00).
An International Digital Stamp is set to launch later this month.