It is spending about €53 million plus VAT on a Falcon 6X that is built in France.
The aircraft can reach the west coast of the United States without refuelling because of its more than 5,000 nautical mile range.
The Learjet, the government's former aircraft, was known to have issues.
Late last year, it broke down several occasions, trapping then-taoiseach Leo Varadkar in Paris in November 2023 and forcing then-higher education minister Simon Harris to abruptly cancel a plan to use the jet to attend a meeting in Brussels in December 2023.
In 2024, the 30-year-old Learjet was only utilised for medical evacuations.
The Falcon 6X is "intended as a replacement to the Learjet" and will perform all of the tasks that the jet had previously performed, according to a Department of Defence spokeswoman.
The Irish Government have agreed to acquire a Dassault Falcon 6X
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According to a Department of Defence release, a contract for the new multipurpose aircraft that would be utilised "in overseas missions across the globe" has been awarded.
It is anticipated to be accessible in the second half of 2026, just in time for Ireland's EU Presidency.
The new Government jet is "a game-changer for the State’s transport, airlift, and medical capabilities," according to Tánaiste Micheál Martin.
"It will be used for a wide range of tasks, including the non-combatant evacuation of Irish citizens from critical situations, air-ambulance patient transfers, medical evacuation or repatriation of Irish Defence Forces personnel deployed on overseas missions and logistics support for the transport of supplies to Irish Defence Forces overseas missions," said Martin.
The Falcon 6X, which is built by the French aerospace company Dassault Aviation SA, has a passenger capacity of 14 and can accommodate up to 17.
The Irish Air Corps will fly it out of Baldonnell's Casement Aerodrome.
The airframe is presently being constructed at the company's Bordeaux, France, production site.