Marc Jacobs, 50, and his muscle-bound boyfriend Harry Louis

Marc Jacobs, 50, and his muscle-bound boyfriend Harry Louis, 24, lock lips during romantic trip 

Marc Jacobs might well be celebrating his half century, but it doesn't appear that he's prepared to slip into comfortable dotage just yet. 

The fashion designer is in Rio to mark turning 50, but looks and acts years younger thanks in part to the ever presence of his younger boyfriend, Harry Louis.

The 24-year old porn star hasn't ventured far from his handsome and well built partner's side as they enjoy a break in Harry's native Brazil to mark the big occasion. 

Lip lock: On Wednesday, Marc Jacobs and his boyfriend Harry Louis were seen kissing during a boat ride in Rio de Janeiro where the couple is celebrating Marc's fiftieth birthday

Say cheese! The couple leaned in to take a cute snapshot with each other in front of the beautiful landscape

On Wednesday, the lovers were seen locking lips as they took a romantic boat ride with some friends.

Taking a break from their intimate embrace, the duo also snuggled up next to each other to pose for some pictures, documenting the milestone moment.

And although Harry wasn't seen lighting up on the water, Marc enjoyed a leisurely cigarette as he stood in his plaid shorts and tight black V-neck tee. 

But he didn't stay covered up the whole trip.

Cigarette break: The fashion designer took some time to light up between kissing and taking pictures

So handsome: Harry Louis (L) and Marc Jacobs (R) stroll hand in hand along the beach in Rio

On Thursday, he revealed his rock hard body as he and his beau walked hand-in-hand on through the powdery sand at Ipanema beach in Rio.

Marc looked incredibly muscular, and his obliques rippled from beneath his tight black shorts, making a defined 'V' shape. 

His boyfriend was in equally good shape, and showed off his rippling torso and toned pectorals as he strutted along the beach in a pair of metallic trunks.

Pucker up: Marc and Harry share a tender moment on the beach in Brazil during their romantic holiday 

Larking around: Marc and Harry were playful in the surf, and clearly really enjoying being together 

At one point he turned and gazed lovingly at New York born Marc, peering at him sweetly from behind dark oversized sunglasses.

Harry kept his wavy dark hair under a backwards baseball cap, and his dark beard highlighted his strong jawline.

He was clearly enjoying celebrating the milestone birthday with Marc, who he is thought to have met in London a few months ago.

Initially, the pair refused to confirm or deny reports that they were dating.

On a natural high: Marc and Harry posed for a photo as they sunbathed on a roof

Smooth sailing: Marc Jacobs (R) and Harry Louis are in Brazil to celebrate the designer's 50th birthday 

A photograph of the famed designer looking cosy at a Paris party with the adult film actor led to much-hyped speculation about the nature of their relationship.

According to Brazilian gossip site GPSBrasilia, Jacobs met the youthful and exotic-looking Mr Louis in the British capital.

Born in Brazil, Louis began his sizzling career in Spain and in 2006, after supposedly having his heart broken, moved to the United Kingdom.

He now has over 4000 followers on Facebook and fans of his English language blog regularly log on to catch up on news about his work and look at family photographs.

They may also enjoy Louis gushing about his love for his mother, who - he says - is his best friend.

Milestone birthday: Marc Jacobs is taking an extended break in sunny Brazil with his boyfriend and other pals

Save a slice for us: Marc and Harry pose with a special birthday cake, complete with dogs made out of icing 

It is not known if Marc has met Harry's beloved mum yet, but if she follows her handsome son on Twitter then she will have an idea of what they have been getting up to on their holiday. 

Harry has posted a string of Twitter pictures of him and Marc soaking up the sunshine and celebrating his birthday.

In one picture, the couple are sunbathing on a roof, and in another looking out from a balcony over crystal blue waters.

Check him out: Marc wears a pair of plaid shorts as he gazes out at the beautiful views from a balcony

Blue skies: Marc and Harry have been enjoying the Brazilian climate with plenty of sunbathing sessions

Loved up: Marc looks content as Harry leans in for a tender kiss in this photo posted to Twitter

In another snap, the pair seem to be on some sort of boat, and Harry is tenderly kissing his serene looking man. 

To mark the actual birthday, they enjoyed dinner with Brailian actress Mariana Ximenes, who Harry said organised 'a very beautiful and unforgettable night.' 

In some of the pictures, she can be seen wearing a purple dress and smiling broadly as she enjoys socialising with the handsome couple.

Also in the pictures wearing a pale shirt is actor Reynaldo Gianecchini, who Harry describes as 'such a fun guy'.

An unforgettable night: They enjoyed a meal with actress Mariana Ximenes (R) and actor Reynaldo Gianecchini

One hell of a cake: Marc is presented with a cake made by one of Harry's Brazilian friends 

Happy days: Marc Jacobs is having a ball celebrating his milestone birthday in Brazil with his younger boyfriend