Speculation arose after Calder was snapped with a band on her ring finger while at Nice airport with the 'What Makes You Beautiful' singer.
It was also noted by The Mirror that the couple were returning from a romantic getaway in France and Tomlinson's sister had recently tweeted about having Calder as her sister-in-law.
However, Simon Jones of One Direction PR firm Hackford Jones dismissed the story on Twitter today, simply writing: "@3am Louis and Eleanor are not engaged."
Tomlinson previously praised his model girlfriend for being "really down to earth" and defended her when One Direction fans sent malicious messages on Twitter.
The pair were first romantically linked back in September.
One Direction in pictures: