The couple, who had been dating for over a year, are said to have ended their romance after disagreeing about their future together.
It's thought Louis isn't ready to settle down and commit, whereas Lucy is.
News of the pair's break up was revealed in The Sun. An insider told the paper: "Lucy and Louis wanted different things... In the end, Lucy wasn't prepared to wait."
They added: "Louis really had led Lucy on in that they'd discussed marriage and kids at length. It came like a bolt out of the blue and doesn't really make any sense to her."
So far, neither Louis or Lucy have commented on such reports.
If the pair have split, Lucy and Louis going their separate ways will come as a shock to fans, as the duo had seemed pretty smitten together.
Both Lucy and Louis were often spotted gushing about each other, and the Olympic medallist had previously said he could see himself having children with Lucy.
Louis had said in June last year: "Lucy is a big part of my life now. I don't know where that's going to go, but hopefully it will be a situation where I've got some little Lucys running around."
Just last month, the couple had enjoyed a trip to Thailand to celebrate their first anniversary together. The pair began dating on New Year's Eve.
Marking twelve months of dating, Lucy had gushed about her beau, telling fans she was looking forward to the year ahead.
She tweeted: "Hope u all have a fantastic night tonight!!! Me & Louis will be celebrating a few hours earlier than all of u in the uk. It's our 1 year anniversary at midnight. Can't believe I've put up with him for a WHOLE YEAR. Jokes, love him to bits. Bring on 2016!"
Lucy and Louis initially met while both starring on BBC gymnastic show Tumble. They claim romance didn't blossom until the show wrapped up and first went public with relationship in January 2015.
Reveal has contacted a rep for Lucy.
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