Gatland has been long linked with the position and will today be announced as the man who will lead the Lions on their 2013 tour of Australia.
The 48-year-old was meant to be revealed at the new coach for the team in April but the planned appointment was postponed after he broke both his heels in a fall.
Gatland has been the outright favourite to succeed Sir Ian McGeechan for over a year now and becomes the second man from New Zealand to ever coach the Lions.
He will immediately start his Lions commitments and will not coach the Welsh side at next year's Six Nations tournament.
Graham Rowntree and Shaun Edwards are expected to be made Gatland's assistants, but those appointments won't be announced until October ahead of next year's three Test matches and six warm-up friendlies down under.