“I feel, and in consultation with Cricket Ireland, that now is the right time to hand over that mantle.”
Porterfield, who intends to keep playing international cricket, led the senior Irish side 253 times across all forms of the game since taking over from Johnston.
He led Ireland in two 50-over World Cups and five T20 World Cups, but perhaps his most significant moment as captain was leading Ireland out at its historic first-ever Test against Pakistan in Malahide in May 2018.
“There have been many highs, along with a few lows along the way, but I can honestly say that it has been thoroughly enjoyable,” he said.
Leinster batsman Balbirnie, who will take over the Test and ODI teams, played his first one-day international against Scotland in 2010.
He played in Ireland’s first Test against Pakistan but the 28-year-old failed to score a run in either innings, becoming the 44th player in the history of Test cricket to be dismissed for a pair on debut.
“The selectors have made a great choice in appointing ‘Balbo’,” said Porterfield. “Having spoken to him, I know how honoured and excited he is to get going.