Both countries were confirmed as full members after a unanimous vote at an ICC Council meeting
The move, which means the two countries become full members of the ICC, cricket's global governing body, takes the number of Test-playing nations from 10 to 12.
Both countries were confirmed as full members after a unanimous vote at an ICC Council meeting during its annual conference in London on Thursday.
Now Ireland and Afghanistan's men's teams will be eligible to play five-day Test cricket, widely regarded as the sport's pinnacle format.
Ireland have established themselves on the international scene during the course of several World Cups, recording wins over Pakistan, the West Indies and England.
Afghanistan's progress has been even more rapid, with many Afghans' first contact with cricket taking place during the 1980s and 1990s, as refugees fled to Pakistan to escape the Soviet invasion.
The ICC announced the establishment of cricket's 11th and 12th Test nations with a statement via its Twitter feed saying: "@ACBofficials and @Irelandcricket confirmed as Full Members after a unanimous vote at ICC Full Council meeting.
"Both will now be eligible to play Test cricket following a recommendation that their applications met newly approved member criteria."
Bangladesh were previously the last country to be granted Test status in 2000.
But Afghanistan and Ireland have now joined an exclusive club that also includes founder members Australia and England, who played the first Test match at Melbourne in 1877, South Africa, New Zealand, the West Indies, India, Pakistan, Sri Lanka and Zimbabwe.
Ireland international Gary Wilson welcomed the news with a statement on his own Twitter feed, saying: "An historic day for Irish cricket.
"Years worth of work feels like it has been recognised. There are many people in the background that have made this happen. Current officials, players and management have been major cogs but let's not forget the tireless volunteers who worked so many years to get us where we are.
"Men who played for free and managed for free...As well as for us, this is for them."
Earlier this week, ICC chief executive David Richardson had been optimistic both Ireland and Afghanistan's applications for Test status would be approved, telling reporters they were "very well founded".