Who is Jeopardy! contestant Ron Lalonde, who ended Libby Jones's streak?

Jeopardy! season 42 saw a familiar face on the 63rd game, which premiered on Wednesday, December 3, 2025, when Ron Lalonde entered the stage, the identical twin brother of another Jeopardy! champion, Ray Lalonde.

Born and raised in Thunder Bay, Ontario, Ron Lalonde is a medical physicist from Pittsburgh, Pennsylvania, who became the second twin in his family to win Jeopardy! on Wednesday night, earning $15,201 from the single win, beating Libby Jones.

Ray Lalonde made an impressive 13-game streak on the show nearly three years ago in December 2022, claiming the title of super-champion (a player who wins at least 10 games) and went on to compete in the 2023 Tournament of Champions.

Now, Ray stands in the top 20 on Jeopardy! players of All-Time Regular Play Only at number 13, as one of the greatest of all time, winning a total of $386,400.

“Your twin brother, Ron, called you the real ‘Jeopardy!’ talent in the family. And here you are,” Host Ken Jennings said later, adding, “Those are big shoes, though.” Jon replied, "Very big, yes...No pressure at all.”

Jennings asked Ron during contestant interviews to prove he was really Ron and not Ray on the Alex Trebek Stage. "Ray’s actually in the audience," Ron said, pointing toward his twin. Ray waved back to the host with a smile, who greeted him with Ron joking about their resemblance:

"Honestly, our brothers and sisters are even smarter than us. They’d crush it on this show."

Who is the twin brother of Ray Lalonde, who became a champion on Jeopardy! season 42?

Ron Lalonde is a distinguished medical physicist who works in Pittsburgh, where he serves as the Chief Physicist at UPMC Shadyside Hospital and teaches as a clinical associate professor in the Department of Radiation Oncology at the University of Pittsburgh.

His work also extends across the UPMC Hillman Cancer Center network, where he oversees radiation oncology physics operations and helps guide residency training and quality-assurance programs.

In his early years at the Nomos Corporation, he played an important role in developing some of the first commercial tools for IMRT (intensity-modulated radiation therapy) and IGRT (image-guided radiation therapy).

He earned both his bachelor’s and master’s degrees at the University of Waterloo, where he studied biophysics specialization in fluorescence and ultrasound imaging.

Ron later completed his PhD at the University of Toronto, where he researched acoustic techniques for ultrasound hyperthermia.

His research focuses on developing treatments that are more accurate, efficient, and personalized, leading to projects in radiosurgery planning, quality assurance, and knowledge-based planning, including serving as principal investigator on a grant evaluating Varian’s RapidPlan system.

Ron Lalonde made his debut as a contestant on Jeopardy! on Wednesday when he played against two-game champion Libby Jones from Florida and Sarah Murphy, a freelance transcript editor from Hamilton, Ontario.

He defeated Jones, who was the giant killer, for being the reason for the end of champion Harrison Whitaker's 14-game run on the show. He answered correctly in the Final Jeopardy! by writing "Poet’s Corner," while Libby answered incompletely, writing just "Poet."

The final clue from the category "Monuments & Memorials" in season 42, game 63 of Jeopardy! was:

In NYC’s Cathedral of St. John the Divine, an alcove with memorials to Hart Crane, Sylvia Plath & 54 others is the “American” this.

Stay tuned for more updates.