Speed named new Wales boss
The 41-year-old has limited managerial experience having taken the reins of Championship side Sheffield United only in August.
Speed replaces John Toshack who resigned in September following a Euro 2012 qualifier defeat to Montenegro.
"It is impossible to turn it down when your country comes calling," he told a news conference. "I am a very proud man to be manager of Wales.
"I am disappointed to leave Sheffield United because I felt I had a job to do there and I was fully committed, but I have made the decision and I feel in my heart it is the right one."
Speed, who won 85 caps for Wales during a 14-year international playing career, will need to revitalise the team after their poor start to the Euro 2012 qualifying campaign.
Wales are bottom of Group G with three defeats from their opening three matches.