Pop star sisters Kylie and Dannii Minogue have enthralled viewers with an infectious disco duet in their first television reunion in Australia for three decades.

The singing siblings who have sold more than 80 million records between them took viewers back in time when they belted out an original disco track, ‘100 degrees’, during the X Factor grand final on Tuesday night.

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The single, about a hot Aussie Christmas Day, is off Kylie’s new album, Kylie Christmas.

Social media lit up with excitement as the sisters in twin mirrored dresses – Kylie in pink and X Factor mentor Dannii in blue – took to the stage.

“Holy Minogue that was bloody fantastic,” Dale Roberts posted.

The toe tapping ditty was a long overdue duet for the Minogues who last performed together in Australia for a Young Talent Time concert back in 1986.

Kylie and Dannii’s parents were watching on in the live audience.

Kylie said sharing the stage with her sister was a “very special moment”.

Wollongong’s Cyrus Villanueva, 19, won X Factor 2015 on Tuesday night, beating Sydney duo Jess Dunbar and Matt Price, both 24, and Louise Adams, 31, from Mt Gambier.