The New Zealander previously held the role in 2013
Warren Gatland will lead the British and Irish Lions for the second tour in a row, after being confirmed as head coach for the 2017 tour to New Zealand.
The Wales head coach called the opportunity "a massive honour". He will become the first Lions coach to lead the side in a test series against his native country.
Gatland was the unanimous choice of the Lions committee it was admitted. He becomes the first foreigner to lead the Lions on two separate tours.
The 52-year-old revealed he "wants some continuity" with the backroom staff. Ireland coach Andy Farrell was part of Gatland's assistants in Australia in 2013 and may be called upon again. His assistants will be announced later this year on December 7th.
Although still contracted to the Welsh Rugby Union, Gatland begins his role with the Lions straight away. He travel to New Zealand on Thursday to begin preparations and scout appropriate training bases for the team.
The Lions will play ten matches in New Zealand next summer, beginning with a tour match against the New Zealand Barbarians on June 3rd in Whangarei. The First Test takes place in Auckland, three weeks later.
New Zealand have won nine of the last ten tests between the two sides, and have won the last four test series between the sides.