Howley steps into Gatland's shoes
Gatland has been named coach of the British and Irish Lions for a second time - taking them on a 10match tour of New Zealand next year.
He has been seconded from his role with the Welsh Rugby Union from September 1, through to the conclusion of the 2017 Lions tour.
Howley takes up the role of Wales coach, with full responsibility for the senior team, with immediate effect.
The first task up for the former Wales captain and his experienced coaching team is the November Tests against Australia, Argentina, Japan and South Africa.
"I'm delighted, proud and extremely excited to be named Wales coach for this period," Howley said.
"I would like to congratulate Warren on his thoroughly deserved selection and the honour of being named the coach for a second successive Lions tour.
"I thoroughly enjoyed the experience of being the [Wales] coach in 2012 and 2013 and I'm excited to have the challenge once again and I would like to thank the WRU for this opportunity."
Howley joined Wales as an assistant coach in 2008 and has previously led Wales for spells as head coach in 2012 and 2013.
Wales clinched the 2013 Six Nations title under his guidance.
"We would like to congratulate Warren on the appointment and the honour of leading the British & Irish Lions for a second consecutive tour," WRU Group Chief Executive, Martyn Phillips said.
"The appointment is recognition of Warren's standing in the game and we are proud to support his role. We are delighted to appoint Rob as head coach of Wales for the period that Warren is away. Rob is a very experienced international coach and forms part of one of the most experienced coaching teams in the international game.
"We considered a range of options domestically and overseas when contingency planning for this eventuality and determined that Rob represents the optimum appointment for Wales.
"Rob's experience and relationship with the Regional coaches affords the opportunity for a joined up approach, which will be of an important benefit for the game in Wales.
"The opportunity for coaches to continue to develop and learn is critical for our future success. It is important we have a strong Welsh contingent to our coaching team and that learning on the international stage benefit the game here in Wales.
"These appointments allow our coaches not only use their experiences but to continue to develop at the very top end of the game.
"I know Rob is excited and will thrive and learn from the experiences that the role will bring.
Warren Gatland added, "Rob's appointment is great news for the squad.
"We have an experienced management team in place and Rob's international experience as a coach and his desire to continue developing is a great mix to drive the squad forward."