Sir Elton John and his partner David Furnish have formally converted their civil partnership to a marriage - with the musician documenting the day on the Instagram website.
The couple have been hosting a ceremony at their Windsor estate in Berkshire with a number of stars in attendance.
David and Victoria Beckham, musician Ed Sheeran and actor David Walliams were among the guests.
Mr Furnish and Sir Elton, who have two sons, became civil partners in 2005.
The couple's sons Zachary, who was born in 2010, and Elijah, born last year attended the ceremony.
One image - showing the newlyweds holding hands, with Elijah standing between them - bears the caption: "Zachary grabs David's iPhone and takes a photo of his brother while we exchange our vows."
Sir Elton has been including the hashtag #ShareTheLove on his posts on Sunday.
Friends of the couple have also been using the tag, with the Beckhams' eldest son Brooklyn writing: "Amazing day with family and special friends congratulations Uncle Elton and Uncle David #ShareTheLove."
The teenager posted a photograph of the wedding lunch menu, which included wild mushroom soup with truffle cream, beef short rib and caramelised onion pie and warm chocolate pudding with ice cream. Guests were served Laurent-Perrier champagne.
Sir Elton has posted a number of pictures to the photo-sharing website, where he has thousands of followers, including a picture taken at a window showing a garden, with the caption: "Good morning! Nice day for a wedding".
He later wrote: "The tables look stunning! We had red roses at our Civil Partnership 9 years ago and they brought us so much luck."
On 21 December 2005, they held a civil partnership ceremony at the Windsor Guildhall.
In March, the law was changed in England and Wales to allow same-sex marriage.
Sir Elton said at the time he was "very proud" of Britain for changing the law.
"Having our civil partnership was an incredible breakthrough for people that have campaigned for a long time - through the 60s and the 50s in England when it was so hard to be gay and hard to be open about it. And it was a criminal act.
"So for this legislation to come through is joyous, and we should celebrate it. We shouldn't just say, 'Oh, well we have a civil partnership. We're not going to bother to get married'. We will get married."
Celebrities gave their reaction on Twitter. Gary Barlow wrote: "What an incredible day." Graham Norton said: "Huge congratulations to Sir Elton John and David Furnish. Married at last!!"
Walliams said it was a "magnificent" day, while Hugh Grant tweeted: "Groom Groom - Britain races into the future. Congrats Elton and David. Congrats enlightened UK."
Guests also included singer Lulu, Burberry chief executive Christopher Bailey, as well as comedian Jimmy Carr who tweeted: "#ShareTheLove at the beautiful wedding of two beautiful people. Wishing Elton & David every happiness. X".