The couple made history on December 21, 2005, as they were the first to be legally pronounced civil partners at Windsor Guildhall in southeast England, and nine years later - when same-sex marriage was legalised in the UK - on the same day, John and Furnish converted their civil partnership to marriage during a ceremony at their lavish Windsor estate.
Taking to Instagram to celebrate the milestone anniversary on Sunday, John, 78, captioned a shot of him and Furnish at their civil partnership ceremony with: "Happy anniversary to my incredible husband, @davidfurnish.
"Today we celebrate 20 years since our civil partnership, 11 years of marriage, and many more years of happiness to come! (sic)"
Artist Furnish, 63, also took to his Instagram account to pay tribute to his singing icon spouse as he shared two images from his and John's civil partnership.
He captioned the photos with: "20 years ago today we were civil partnered. 11 years ago today we were wedded. Happy Anniversary to my magnificent husband @eltonjohn. I'm so grateful for the beautiful life we have built together. Love you forever."
Celebrities and fans rushed to send their love for the smitten couple.
Actress Nicola Peltz Beckham, 30 - who married former model Brooklyn Beckham, 26, in 2022 - penned: "Most beautiful love!! I love you both so much (sic)."
Actor-and-model Damian Hurley, 23, wrote: "Heaven. Love you both endlessly xx (sic)."
And 67-year-old singer Belinda Carlisle - who is married to 70-year-old actor-and-film producer Morgan Mason - said: "Happy Anniversary!!! We celebrated 41 years today. Love is grand. (sic)"
John and Furnish - who met at a dinner party hosted by the Rocketman singer at his house in 1993 - became dads in 2010 when they welcomed Zachary, 15, into the world, via a surrogate.
And in 2013, son Elijah, 12, joined the family, also through the same surrogate.
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