Robert Downey Jr and his wife Susan are celebrating their 17th wedding anniversary this weekend, and to mark the occasion, the Hollywood actor decided to share a never-before-seen photo from their big day.MORE: Ben Affleck reveals real reason he and Jennifer Lopez called off 2004 weddingTaking to Instagram, the Iron Man star posted a photo taken shortly after they exchanged vows back in 2005. It shows Robert, then 39, dressed in a black suit and a purple spotted scarf cosied up to his 30-year-old bride, who is wearing a stunning plunge neck wedding gown and veil.WATCH: Robert Downey Jr speaks to HELLO!"Today marks 17 years of unadulterated marital bliss," the caption read. "Susan, you are my bedrock, touchstone and lucky stars to boot."MORE: Robert Downey Jr opens the doors to his fun family home – take a lookMORE: Celebrity engagements of 2022: Simon Cowell, Michelle Dockery and moreThe couple exchanged vows in a Jewish ceremony in the Long Island town of Amagansett, New York, surrounded by a star-studded selection of friends and loved ones, which included Keanu Reeves, Sting and Ellen Barkin.A post shared by Robert Downey Jr.