The 30-year-old Saracens lock becomes the first Black player to captain the Lions and only the third Englishman in 89 years to be appointed leader of the touring side.
One of the few sure Test starters, Itoje will be embarking on his third Lions tour after being selected as the youngest player in New Zealand in 2017 and playing a standout role in South Africa in 2021.
Appointed England captain in place of Jamie George in January, Itoje led his country to second place in this year's Six Nations Championship with four wins in a row.
The Lions have a game against Argentina in Dublin on June 20. They will have five tour games before the first test in Brisbane on July 19. The second and third Tests are on July 26 and August 2.
The first Englishman to lead the Lions since Martin Johnson 24 years ago, and only the second in the professional era, the London-born son of Nigerian parents was the obvious choice after Ireland captain Caelan Doris suffered a shoulder injury.
Itoje showed he was captain material from an early age, leading the England Under-20s to Junior World Cup triumph in 2014, though he became Saracens captain only this season.
"It feels amazing to be named Lions captain," said Itoje, who revealed that he found out the news when Farrell called him on Tuesday.
"I'm deeply honoured, humbled and I'll do my best to do the role justice. I'm very much looking forward to the challenge ahead, it's going to be a great tour.
"I know the appetite amongst the players is extremely high, everyone is hungry to be a Lion and I can't wait to play my role."
With Reuters
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