The post was soon met with a downpour of adoration, with fellow actress Sara Wiseman deeming the couple "dreamboats" in the comments.
"Then and now," she added. "Hugest congratulations you two. ❤️❤️❤️❤️❤️❤️❤️."
"Happy Anniversary 🥂May you always shine together. 💕⭐️," a second user wrote.
"Congrats to you both it was a marriage that was meant to be and will live a life time ❤️," a third penned.
Rebecca and Richard originally met on the set of Aussie TV movie Dogwoman in 1999 - but their story goes back much further than that.
"In walks this beautiful, tall New Zealander who happened to live on the same street as me when I was five," the Back To The Rafters actress told Woman's Day last month about her and Richard's first meeting.
Two years later, the couple tied the knot on a beach in Thailand before welcoming their son, Zachary, three years after that.
For Rebecca, above all else, respect is a big pillar of their relationship.
"You must respect each other... it's having complete and utter respect above all else and obviously love and being willing to compromise, which is what we've always done," she told the publication, adding that Richard is "my rock, he's my everything".
"It doesn't mean we don't have issues, but we always work through them because I can't imagine growing old with anyone else."
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