“Queen of The Metropolitan Opera” Mercedes Bass and billionaire Sid Bass are divorcing after 23 years, with sources telling us, “This is the biggest high-society divorce — since their last divorces.”

The Bass romance blossomed when Mercedes was married to Ambassador Francis Kellogg and Sid to Anne Bass. Mercedes famously got Sid’s attention by throwing a bread roll at him at a 1986 lunch in East Hampton.

Creating a huge scandal, Sid, the scion of a Texas oil family, divorced Anne with a settlement said to be between $200 million and $500 million.

Mercedes and Sid married in 1988 at The Plaza, becoming the toast of New York society and big patrons of the Met Opera, to which she personally donated $25 million.

But on Thursday, they released a joint statement that they “mutually agreed to end their marriage” and they “continue to love each other and remain good friends.”

One source told us Sid, 69, is tired of attending black-tie events and has taken up painting, while Mercedes, 67, continues in society life.

The source explained, “They are leading separate lives. He’s had it with the black-tie and the opera, and wants to retreat and work on his art. She has informed the Met board of her divorce, and insists she will stay active.”

Sources say the split wasn’t totally unexpected. The New York Social Diary last year reported the couple would not spend Christmas 2010 together. Mercedes appeared last week at the season opening of “Anna Bolena” at the Met without Sid but accompanied by Nancy Kissinger.

Sid Bass, worth an estimated $2.1 billion, is a son of Perry Richardson Bass, who built an oil fortune with his brother Sid Richardson.

This divorce will undoubtedly be just as expensive as Sid’s last. The couple have an apartment at 4 E. 66th St., a $16 million estate in Fort Worth, Texas, and a residence in Aspen, Colo. Their lawyers didn’t get back to us.