Robert Irwin faced a heartbreaking milestone on Thursday – the anniversary of his father Steve’s death in 2006.

But the young star put on a brave face as he left rehearsals for Dancing With The Stars US in Los Angeles.

The 21-year-old Wildlife Warrior beamed and waved at photographers as he walked with his bodyguards, following another gruelling day in the rehearsal studios.

Looking ready for action, Robert wore a sporty blue T-shirt and grey joggers, while covering his eyes behind a pair of aviator sunglasses.

He completed his look with white sneakers and slung a yoga mat and tote bag over one shoulder.

At one stage, he threw a thumbs-up to onlookers before being ushered away by his entourage.

Robert Irwin, 21, (pictured) put on a brave face as he left Dancing With the Stars US rehearsals in Los Angeles on the anniversary of his father’s death on Thursday

The Wildlife Warrior beamed and waved at photographers as he walked with his bodyguards, following another gruelling day in the rehearsal studios

He was not joined for the outing by his stunning dance partner Witney Carson, who bears a striking resemblance to Robert’s ex-girlfriend Rorie Buckey.

Eighteen years have now passed since the Crocodile Hunter was fatally struck by a stingray barb during a filming expedition on the Great Barrier Reef, a moment that shocked the world and changed the Irwin family forever.

Robert, who was just two years old at the time, has since followed in his father’s footsteps, becoming a passionate conservationist and TV personality.

His mother Terri and sister Bindi have also continued Steve’s work by expanding Australia Zoo.

Later on Thursday, Robert commemorated the anniversary of Steve’s death with a heartbreaking Instagram post, sharing a photo of himself as a toddler playing with a lizard alongside his father.

‘You never stop inspiring me,’ he captioned the image, prompting an avalanche of heartfelt messages from his fans.

‘A great man. So glad you are continuing his legacy!’ one user wrote.

‘Awww my heart!!! He’s so proud of you,’ another added.

Looking ready for action, Robert wore a sporty blue T-shirt and grey joggers, while covering his eyes behind a pair of aviator sunglasses

He completed his look with white sneakers and slung a yoga mat and tote bag over one shoulder

Robert’s appearance on the competitive dancing series marks a decade since his sister Bindi’s triumphant win on the show in 2015 alongside her dancing partner Derek Hough

Meanwhile, Robert is working hard ahead of his appearance on Dancing With The Stars US, competing against the likes of Hilaria Baldwin, Corey Feldman and Alix Earle.

His stint on the series was revealed in April, following his smouldering American ad campaign for Bonds.

The Aussie TV star was officially confirmed to be appearing on the show by Variety – and appeared in high spirits as he landed in Los Angeles ahead of filming.

Robert’s appearance on the competitive dancing series marks a decade since his sister Bindi’s triumphant win on the show in 2015 alongside her dancing partner Derek Hough.

Eighteen years have now passed since the Crocodile Hunter was fatally struck by a stingray barb during a filming expedition on the Great Barrier Reef, a moment that shocked the world and changed the Irwin family forever. Pictured: Steve and Terri Irwin with their children Bindi and Robert in 2003

Later on Thursday, Robert commemorated the anniversary of Steve’s death with a heartbreaking Instagram post, sharing this photo of himself as a toddler playing with a lizard alongside his father