Michael Douglas and Catherine Zeta-Jones have celebrated 25 years of marriage.

The Wall Street actor and Chicago star, who were introduced by Danny DeVito at a film festival in France in 1998, married at the Plaza Hotel in New York City on 18 November 2000.

Taking to Instagram on Tuesday, Michael shared a throwback photo of himself and Catherine to celebrate the milestone.

"Happy 25th anniversary, my darling Catherine. Who knew? All my love, Michael," he wrote in the caption.

In addition, Catherine shared her own message in honour of her "sweetheart" husband.

"Twenty-five years ago today, I walked down the aisle. The intoxicating aroma of flowers, the glow of the candles, the resounding harmonious Welsh choir and you at the end of the long walk waiting for me, looking at me the way only you can," she wrote. "I love you today as I did then. Thank you, sweetheart."

Catherine added a slideshow of photos showing herself and Michael, 81, over the years, including a series of snaps from the couple's nuptials.

The 56-year-old also revealed that there was a Welsh flag placed outside the luxury venue in honour of her heritage.

Michael and Catherine share two children: son Dylan, 25, and daughter Carys, 22.

The Hollywood icon is also father to son Cameron Douglas, 46, from his first marriage to Diandra Luker.