The Duke and Duchess of Sussex shared the warm message in the comment section on Instagram after Kensington Palace posted sweet photos of the tot ahead of his special day.
“Happy Birthday Louis! Sending lots of love from both of us,” the expecting parents wrote via their Sussex Royal Instagram account. The comment concluded with a few birthday-themed emojis and “xo.”
“The Duke and Duchess of Cambridge are delighted to share these new photographs of Prince Louis ahead of his first birthday tomorrow,” the post said. “The photographs were taken earlier this month by The Duchess at their home in Norfolk.”
In a separate Instagram post, the couple shared another photo of their child and wrote: “Happy Birthday Prince Louis!”
Prince Louis is fifth in line to Britain's royal throne, behind grandfather Prince Charles, father Prince William, big brother Prince George and big sister Princess Charlotte.
Fox News’ Jennifer Earl contributed to this report.