Louis, 24, and Danielle, 21, sported matching Red Bull-emblazoned jackets, as they were likely unprepared for the unfortunate weather in the Mediterranean location
The One Direction star and father-of-one, had no qualms about showing off his love for his pretty brunette girlfriend, 21, as they posed against the stunning backdrop of the Mediterranean coastline.
News that Louis was to become a first-time dad broke in July 2015, following his brief fling with Briana in Los Angeles the previous May.
He is now fully loved-up with Danielle, a budding actress with whom he has spent plenty of time since going on hiatus from boyband One Direction.
The smitten pair appear to be making the most of their European jaunt: after arriving in London on Friday from Los Angeles, they headed straight to Monaco and were seen enjoying a spot of nicer weather on Saturday.
Earlier in the day the pair paid a special visit to the Red Bull Racing garage along with Manchester United star Michael Carrick and New Zealand rugby ace Dan Carter.
Boyband star Louis donned a simple pair of black skinny jeans and a Red Bull-emblazoned waterproof jacket, and Originals actress Danielle sported the same cover-up.
But she still showed off a hint of her glamorous side with a long, flowing black maxi skirt and pretty tan fringed strappy sandals on her feet, and her brunette mane styled into loose, bouncy waves.
During the day, History hitmaker Louis was also seen rubbing shoulders with his footballer player pal Michael Carrick, and Australian driver Daniel Ricciardo.
And Danielle also posted a fun Instagram snap as the evening drew in, showing her covered in the hood of her protective coat while joking about the damp conditions.
Pouting into the lens while taking the shot, she wrote: ‘Raining at the races.’