O.J. Simpson trial witness Kato Kaelin and his wife, Nan Xue Kaelin, are ending their marriage after less than 5 years together ... TMZ has learned.

According to docs, obtained by TMZ ... Kato and Nan filed a joint petition for dissolution in Los Angeles County Superior Court on Wednesday.

The couple got married on September 17, 2021, and separated on August 1, 2025, according to the docs.

The pair have no minor children together, no interest in real property and no community assets or liabilities to divide. The filing also states both parties waived any right to spousal support.

Kato tells TMZ … "Nan is the most wonderful and beautiful woman in the world. We will 4EVER be great friends and have laughter between us. Please respect our privacy."

Of course, Kato has remained a pop culture figure for decades thanks to his connection to O.J.'s murder trial, where he testified as a key witness after staying in Simpson's guest house at the time of the killings.