Which actor played Billy Brennan in Jurassic Park III?

Alessandro Nivola played Billy Brennan in Jurassic Park III.

Billy is a young paleontologist and former student of Dr. Alan Grant. He joins the expedition to Isla Sorna after Paul and Amanda Kirby hire Grant to help locate their missing son, Erik. Billy’s academic relationship with Grant gives the film a mentor-and-protégé dynamic alongside its survival adventure.

The character is also involved in one of the film’s major moral conflicts. Billy secretly takes Velociraptor eggs from the island, hoping to sell them to finance his research. Grant condemns the decision because removing the eggs endangers the nest and helps provoke the raptors’ pursuit of the group. Billy later risks his life to help rescue the others, partially redeeming himself.

Nivola’s co-stars included Sam Neill as Grant, William H. Macy as Paul Kirby, Téa Leoni as Amanda Kirby, Trevor Morgan as Erik Kirby, and Michael Jeter as Udesky. A common mix-up is choosing Macy or Jeter: both are prominent adult characters, but Nivola is the actor credited as Billy Brennan.