Rebecca and Louis were at a taping of ITV gameshow, Keep It In The Family, and it looked like they were both equally thrilled to see one another.
'I Hope' singer Rebecca came runner-up in the seventh series of The X Factor in 2010, during which long-standing judge Louis was on the panel.
Captioning the snap, Rebecca said: "Reunited [heart emoji] X Factor, love this man xx."
Despite his 11-year stint on the panel, Louis is no longer a judge on The X Factor after being replaced by Nick Grimshaw this year. Rita Ora has also replaced Mel B, while Cheryl Fernandez-Versini and Simon Cowell remain on the panel.
The new series has seen a huge shake-up, and not only from the judges. Dermot O'Leary left as main host after eight years, and has been replaced by Olly Murs and Caroline Flack. Meanwhile, Sarah-Jane Crawford left as Xtra Factor host, leaving Rochelle Humes and Melvin Odoom to take her place as new co-hosts.
The second round of X Factor auditions have already kicked off, with more to continue this week in London.
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X Factor's most memorable moments: