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 last night.

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

Kylie and Dannii Minogue sing 100 Degrees together on the finale of The X Factor Australia.
Kylie and Dannii Minogue sing 100 Degrees together on the finale of The X Factor Australia.

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.

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"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 in the live audience.

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

Minogue fan Bree agreed.

"I'm actually gonna start crying because I don't think anyone understands how ICONIC this performance is," she tweeted.

Jaye posted it was great to see such Aussie icons together again while it was all a bit much for some.

Kylie and Dannii Minogue sing 100 Degrees together on the finale of The X Factor Australia.
Kylie and Dannii Minogue sing 100 Degrees together on the finale of The X Factor Australia.

"I love Kylie and Dannii separately but together OMG. My glitter-o-meter just blew up," tweeted @RBFBeauty.

Another social media user, Maddy, wrote: "Well, if that wasn't cruise ship then I don't know what is."

AJ piped up: "What's better than one Minogue? Two Minogues," while @MsShoegal predicted: "This performance will break the Internet and then YouTube in the days to come".

Wollongong's Cyrus Villanueva, 19, won this year's The X Factor, beating Sydney duo Jess Dunbar and Matt Price, both 24, and Louise Adams, 31, from Mt Gambier.

- AAP