A Philadelphia Common Pleas Court judge who has spent nearly two decades on the bench plans to step down in October, two years before the end of her 10-year term.

Lisa M. Rau, 59, appointed in 2001 by Gov. Tom Ridge, did not specify what she planned to do next, saying only in a resignation letter to Gov. Tom Wolf that she was ready “to move on to my next adventure.”

“There has not been a single day as judge over the last 18-plus years when I did not appreciate the responsibility that Philadelphians gave me to serve such a vital role in our justice system,” Rau wrote in her letter, sent Monday.

In emails with The Inquirer this week, Rau, who is married to Philadelphia District Attorney Larry Krasner, declined to elaborate, saying she was preoccupied by a complex and time-consuming mediation. She said a formal announcement would be made in the future.

She added that her decision and its timing were not connected to the career or aspirations of her husband, who has received national attention for his efforts to reduce incarceration and transform the prosecutor’s office. She has spent most of her tenure presiding over civil cases, not criminal matters.

Earlier this week, after the Legal Intelligencer first reported the news of Rau’s impending departure, Krasner congratulated his wife on Twitter.

In an interview Friday, Krasner said that Rau, to whom he has been married for 30 years, “is an incredibly accomplished woman, mother, lawyer, and judge.” He called her “the finest insurgent political candidate I ever saw when she ran for judge,” and said she became “widely regarded as the best judge in the Philadelphia court system at resolving cases.”

A former Peace Corps volunteer in Thailand and a graduate of Stanford Law School, Rau worked as a civil rights attorney before being appointed to the bench in 2001. She was elected to a 10-year term later that year and reelected in 2011. In her letter to Wolf, she said she spent nearly five years supervising “every major civil case filed in Philadelphia’s Common Pleas Court during a calendar year, where approximately 6,000 to 7,000 such cases are filed annually."

In 2002, while overseeing criminal matters, Rau was accused by then-District Attorney Lynne M. Abraham of being anti-police and disrespectful to prosecutors. The city’s judges responded by voting to file a formal complaint accusing Abraham of unethical conduct, and the dispute was resolved privately.

Court spokesperson Marty O’Rourke said Friday that in recent months, four other judges — Amanda Cooperman, Rosalyn Robinson, M. Teresa Sarmina, and John M. Younge — stepped down before the end of their terms.

Replacements have to be filled via appointment, with Wolf, a Democrat, nominating candidates to be voted on by the state Senate, which is controlled by Republicans. Appointees serve until the end of the departed judge’s original term.

J.J. Abbott, Wolf’s spokesperson, said that the governor had not nominated any potential replacements, but that his office would begin discussing those moves with legislators when they return to Harrisburg this fall.

Bob Brady, chairman of the city’s Democratic Party, said Friday that the court also has six vacancies that will be filled when voters head to the polls in November. Brady said churn on the bench is “not abnormal at all,” due to factors including voluntary departures and retirements mandated for judges who turn 75.

The court has 83 judges and seven senior judges, O’Rourke said. Judges are paid $183,184.