Indian-Americans Vanya Shivashankar, 13, and Gokul Venkatachalam, 14, together hoisted the gold trophy amid a flurry of confetti after they clinched the 88th Scripps National Spelling Bee.
Shivashankar, the sister of 2009 champion Kavya Shivashankar, initially oozed confidence as she breezed through such words as cytopoiesis, bouquetiere and thamakau.
Venkatachalam, a basketball fanatic sporting sharp Air Jordans, also tackled such tongue-twisters as poblacion, caudillismo and nixtamal with panache.
But as their eight fellow finalists stumbled one by one, the tension grew until they stood alone on stage at the Gaylord resort by the Potomac River outside Washington.
When Shivashankar, in the fourteenth round, correctly spelled scherenschnitte, the German-derived word for artistic paper cutting, official bee pronouncer Jacques Bailly, broke the news to Venkatachalam.
The contest, Bailly said, was about to run out of words, and if Venkatachalam spelled his next word correctly, he and his rival would be declared joint winners - a repeat of last year's surprise tie.
Word comes easily
The winning word came so easily to the eighth-grader from the affluent St Louis, Missouri suburb of Chesterfield that he skipped the bee contestant's routine of asking for the word's origin, meaning and usage in a sentence.
"N-u-n-a-t-a-k," the devoted LeBron James fan said, spelling the Inuit-derived word for a glacial island as breezily as if he was spelling d-o-g or c-a-t.
Asked afterwards what went through his mind upon hearing the word, Venkatachalam candidly replied: "Me and Vanya are going to be champions."
It was only the fifth time that the National Spelling Bee has ended in a tie since it began in 1925, when gladiolus was the winning word.
It was also the eighth year in the row that American youngsters of South Asian heritage have clinched the title - a trend that on Thursday appeared to provoke fewer racially-tinged posts on social media than last year.
Indeed, of the 10 finalists, seven were Indian-American, and none was more closely watched than Shivashankar, from the little-known Great Plains tech hub of Olathe, Kansas - so much so that the bee featured her prominently on the banner of its official Twitter feed.
It was her fifth time at the bee, where she tied for fifth place in 2013 and 13th place last year, and due to her age it would also be her last chance at spelling glory.
'Dream come true'
"This is a dream come true. I've wanted this for such a long time," said the eighth-grader who lists eating pizza and playing the tuba and piano among her favorite pastimes.
She dedicated her victory to her grandmother, who died last October. "All she wanted was for her grandkids to do well," she said. "I hope she's happy with this."
Coming in third was Cole Shafer-Ray, 14, an eighth-grader from Norman, Oklahoma who fumbled in round four on acritarch, a word for small organic fossils.
Competing for the third year in a row, he came across as a poor sport when he ducked a consolation kiss from his mother and went all-in for the snack bowl - all seen on live national television.
An American institution, the Scripps National Spelling Bee brought together 285 spellers from all over the United States as well as seven foreign countries.
They were the elite of the more than 11 million youngsters, typically aged nine through 15, who competed in local and regional spelling bees this past school year.
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