The National Football League appointed Roger Goodell as only its fourth commissioner since World War II.
He was elected unanimously by the league's 32 owners after ballots reduced the five-man shortlist to Goodell, 47, and lawyer Gregg Levy.
Goodell served as deputy to the man he is replacing, Paul Tagliabue, and has been given a five-year contract.
"The process has been very good for the National Football League," Goodell, who was the favourite for the job, said.
"The league's got a great foundation on which to build, but I think we've got a lot of challenges to face."
Tagliabue, 65, is stepping down as the league's boss after a 17-year reign which saw the game change dramatically.
Since 1989, the NFL has seen its revenue rise to $6bn from just under $1bn, four new teams arrive, attendances reach record numbers, 22 gridiron-only stadia constructed and healthy relations maintained with the players' union.
Under Tagliabue, the NFL's annual revenue from television alone has increased to an average of $3.7bn.
All these factors helped push team values up tenfold. A recent Forbes magazine article reported that the Washington Redskins, Dallas Cowboys and New England Patriots were now all worth more than $1bn.
But observers say Goodell must now try to raise the sport's profile abroad, develop the league's cable channel and take advantage of new technologies such as wireless and video-on-demand, all while dealing with strong-willed owners.
He will also face calls for tighter doping controls and continue Tagliabue's efforts to get Los Angeles back on the NFL map.
Goodell has spent almost his entire career with the league, starting as an intern in the league office in 1982, and was appointed chief operating officer in 2001.