It's a special day for dads across the UK and Ireland but it's extra special for Prince William as he celebrates his 33rd birthday today.
He is spending his second Father's Day - following the birth of Princess Charlotte on May 2 - with his family including first-born, 23-month-old Prince George.
Last year he took part in a charity polo match with Kate and George in attendance and was spotted taking his first public steps whilst holding on to his mum's hands.
Today is also special for Prince William's mother and father in law, Carole and Michael Middleton, as they celebrate their 35th wedding anniversary.
Just last week the family had an official appearance on the balcony of Buckingham Palace - George's first - to celebrate the Queen's 89th birthday.
And history repeated itself as Prince George wore his father's outfit from the 1984 birthday parade.
The balcony appearance is a royal tradition, and generally follows the Trooping The Colour ceremony.
This was the first time the Queen and three immediate heirs – her son Prince Charles, grandson William and great-grandson George – have appeared together in public.
It also marked Kate's first public appearance since the birth of Princess Charlotte, six weeks ago.
George and Kate spend the following day watching Prince William play polo.