The singer took to Twitter yesterday to complain about messages that were sent to model Eleanor Calder, which showed him with his ex-girlfriend Hannah Walker.
The 'fans' got the phrase 'Louannah' (nickname for Louis and Hannah) trending.
Tomlinson tweeted: "Truth of the matter is its actually not funny in the slightest. I'm reading through some horrible tweets very p*ssed off!"
He first tweeted a message directly to Calder saying: "Love YOU ! xxxx" then added: "I couldn't be happier right now, so let it be :) Thank youuuuu x."
This isn't the first time the band's real-life love interests have been targeted. A girl was reportedly bullied out of going on a date with Zayn Malik by fans who sent her abusive messages on Facebook, and an online hate campaign has been started against Harry Styles's model girlfriend Emma Ostilly.
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Watch a clip of One Direction on iCarly below: