The group, the Buranovskiye Babushki (Buranovo Grannies) from the far-flung Udmurtia region, won Russia's qualifying tournament for Eurovision in the early hours of Thursday with their cheerful folk-disco song "Party for Everybody".
"Party for everybody, come on and dance!" sang in heavily-accented English the elderly group of six women in traditional costumes as the studio audience at the televised qualifying contest clapped along to the beat and cheered with delight, giving them a standing ovation.
The dancing pensioners beat off competition from some of Russia's top pop stars, including a duet by 2008 Eurovision winner Dima Balan and former member of popular female duo Tatu, Yulia Volkova.
Their song is likely to be the first ever sung at Eurovision in a mixture of English and Udmurtian, a language from the Finno-Ugric group.
One of the group, named as "Grandmother Olga", said that all they wanted was to make enough money through singing to build a church in their home village.
"That is our only goal. Grandmothers do not need glory and wealth," she told the Vesti news website.
Russian media reacted with ironic amusement to the choice of a novelty song to represent the country at the glitzy pop extravaganza, which will be held in the Azerbaijani capital Baku in May.
"It's interesting and original, at least," music producer Iosif Prigozhin told news agency RIA Novosti. "They're not young, they're not glamorous, they're in national costumes. They should have gone to Eurovision even earlier."
The Buranovskiye Babushki rose to fame in Russia by singing cover versions of hits such as the Eagles' "Hotel California" and "Yesterday" by the Beatles in Udmurtian, the native language of a region in central Russia best-known for manufacturing Kalashnikov automatic rifles.
Britain has also chosen a pensioner to represent it at this year's Eurovision, the 75-year-old pop veteran Engelbert Humperdinck, best known for his 1960s hit song "Release Me".