Aer Lingus is leasing two aircraft originally destined for a Russian carrier after they became available due to sanctions against the country amid the war in Ukraine.
The new Airbus A320neos were built by Airbus to be delivered to the Russian airline Smartavia in March.
They will now replace two older-generation Are Lingus A320ceos, which will be retired from the fleet.
The 186-seat A320neos are expected to enter into service with the Irish carrier towards the end of July, mainly flying between Heathrow and Dublin.
Aer Lingus continues to expand its fleet and expects to acquire a further two A320neo aircraft next year.
The airline also plans to add six Airbus A321neo XLR aircraft which are a longer-range variant of the A321neo LR, and will enable further growth of its transatlantic network.
Aer Lingus chief executive Lynne Embleton said: “This is a great opportunity to bring new, state-of-the-art aircraft into our short-haul fleet.
“Renewing our fleet is one of the key ways for Aer Lingus to meet our sustainability targets, which is a priority for us over the coming years.
“The new generation Airbus A320neo aircraft is much more sustainable in terms of fuel burn and CO2 emissions and this is not only important to Aer Lingus but also to our customers.
“Equally, these more environmentally-friendly aircraft incur lower landing charges in some key airports so the new A320neos will help us to reduce costs.”