Sir Elton John's ex-wife, Renate Blauel, has launched a legal action against the singer at the high court.
The German-born sound engineer is seeking an injunction against Sir Elton, who she married in 1984.
The couple divorced in 1988, and Sir Elton went on to marry David Furnish, with whom he has two children.
Ms Blauel has kept a low profile since the divorce, but Sir Elton has spoken of his "huge guilt and regret" over the hurt he caused.
The injunction application was filed last week. The trigger for the legal action is unclear, but such measures typically deal with privacy concerns or the publication of personal material.
Ms Blauel's lawyer confirmed papers had been filed but said his client "hopes to resolve the matter privately and amicably".
Sir Elton's representatives declined to comment on the case.
A former flight attendant, Ms Blauel started working in London's Air recording studios in the early 1980s, gaining credits on albums such as Duran Duran's Rio and The Human League's Hysteria.
She met Sir Elton at the studios in 1983, as he recorded his comeback album Two Low For Zero, which included the hit singles I'm Still Standing and I Guess That's Why They Call It The Blues.
The couple married the following year in Australia, with Ms Blauel telling United Press International: "He's the nicest guy I've ever met".
However, they divorced four years later. Sir Elton, who had told Rolling Stone magazine in 1976 that he was bisexual subsequently told the same publication he was "quite comfortable being gay".
In the following years, the pop star and his ex-wife declined to discuss their relationship, despite continued interest from the press.
"For years afterwards, whenever something happened to me, the press would turn up on her doorstep, looking for her to dish the dirt" wrote Sir Elton in his autobiography, Me. "And she never, ever has: She just told them to leave her alone."
The star has only occasionally discussed his first marriage, most notably in a candid Instagram post, written while touring Australia in 2017.
"I'm so excited to be back in Australia for a series of shows," he wrote, alongside a photo from his 2014 wedding to David Furnish.
"Many years ago, I chose Australia for my wedding to a wonderful woman for whom I have so much love and admiration. I wanted more than anything to be a good husband, but I denied who I really was, which caused my wife sadness, and caused me huge guilt and regret.
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I'm so excited to be back in Australia for a series of shows. Many years ago, I chose Australia for my wedding to a wonderful woman for whom I have so much love and admiration. I wanted more than anything to be a good husband, but I denied who I really was, which caused my wife sadness, and caused me huge guilt and regret. To be worthy of someone's love, you have to be brave enough and clear eyed enough to be honest with yourself and your partner. Almost 24 years ago, I met the person with whom I could be fully myself. When we married in 2014, it felt like that fact was accepted by the world. For David and I, being able to openly love and commit to one another, and for that to be recognised and celebrated is what makes life truly worth living. That acceptance and support makes us want to be as kind, responsible and productive members of society, as well as the best parents, that we can be. I love Australia. I love its spirit, its lack of pretence, its passion. I hope it can embrace the honesty and courage that seeks gay marriage as an expression not of desire but of love. #loveislove #marriageequality @davidfurnish
"To be worthy of someone's love, you have to be brave enough and clear eyed enough to be honest with yourself and your partner," he added, before discussing his current marriage and intervening in Australia's equal marriage debate.
In his book, Sir Elton said he had very limited contact with Blauel following their separation, but had invited her to meet his children because "I wanted her to be part of our lives, and us part of hers, in some way.
"But she didn't want to, and I didn't push the issue. I have to respect how she feels."