They also shared a photo of the young prince, captured by Kate Middleton.
“Happy 6th Birthday, Prince Louis! Thank you for all the kind wishes today,” conveyed the Prince and Princess of Wales via their official social media accounts.
The shared photograph showcases a joyful Louis lying on his stomach on the grass in a close-up shot.
This marks the first royal birthday celebration since Middleton and King Charles’s respective cancer diagnoses emerged earlier this year.
Middleton, aged 42, is presently undergoing cancer treatment after her diagnosis. In March, she disclosed that she is undergoing chemotherapy.
Just a month before, in February, Buckingham Palace disclosed Charles’s cancer diagnosis and his commencement of treatment.
The palace has refrained from specifying Charles’s type and stage of cancer or the nature of his treatment.