The former 98 Degrees pop singer out-hoofed pro wrestler Stacy Keibler, who many saw as the favored finalist, along with NFL great Jerry Rice, when ABC's ballroom hit wrapped its second season Sunday night, aired live from Los Angeles.
With his professional dancer-partner Cheryl Burke, Lachey wowed the audience with his number: a freestyle routine danced to "Hound Dog," whose big finish had him vaulting over his partner's shoulders.
"This jump is either gonna make us or kill us," Burke said beforehand.
The couple racked up a total score of 27 (out of a perfect 30) from the three-judge panel. Combined with their score from Thursday's pre-finale, this gave them a total of 87 out of 90.
"From week one, you come out on this floor like Wyatt Earp at the OK Corral," judge Len Goodman praised Lachey.
But it was viewers -- whose vote wielded half the weight -- who clinched his win.
In somewhat of a bombshell midway through the two-hour finale, host Tom Bergeron had disclosed that viewer response eliminated the leggy, blond Keibler and her partner, Tony Dovolani, from the competition. They had held a strong second-place position among the judges with 86 points.
Then, in the program's final moments, host Tom Bergeron made the grand announcement: Lachey was the choice over Rice.
"Woooooooooooooo!" yelped Lachey, who gratefully accepted the "Dancing with the Stars" mirror ball trophy (which he had earlier laughingly described as "ugly").
"Gentleman Jerry" Rice was gracious in defeat.
Asked if he thought he would get this far, he replied, "No, to be honest with you." After congratulating the winners, he thanked his partner, Anna Trebunkskaya, who "kept drilling me, week in and week out."
During the program, all seven of the previously rejected celebrities -- ESPN sportscaster Kenny Mayne, actress Tatum O'Neal, news personality Giselle Fernandez, rap star Master P, actress Tia Carrere, tanned ladies' man George Hamilton and talk-show host Lisa Rinna -- returned for a last dance with their partners.
It was only last January the new "Dancing with the Stars" season had begun with its 10 competitors of sometimes dubious celebrity, and clearly varying skill. Each was paired with a professional dancer for the show's grueling choreography and performance regimen. Then, as the weeks passed, one couple after another was kicked off by joint decision of the judges and viewers.
Receiving a warm welcome from viewers (it ranks seventh in prime time for the season to date), "Dancing" first stepped out as a surprise hit for ABC last summer.
On that season finale, which aired in July, "General Hospital" star Kelly Monaco and her professional partner upset odds-on favorite John O'Hurley, best known for playing J. Peterman on "Seinfeld," and his partner.
But audience complaints arose that the voting process was confusing and that Monaco, star of an ABC soap, got preferential treatment from the network. This prompted a rematch, which, airing in September, gave viewers full sway. The title went to O'Hurley.