Alan Horn, a top creative executive, is the latest high-ranking Disney departure.

One of Hollywood’s senior statesmen announced his retirement on Monday, adding to a startling changing of the guard at the Walt Disney Company.

Alan F. Horn, 78, will step down on Dec. 31 as chief creative officer of Disney Studios Content, a division that includes Marvel, Lucasfilm, Searchlight Pictures, Pixar, 20th Century Studios and Disney’s traditional animation and live-action movie operations. His position is not expected to be filled.

“It’s never easy to say goodbye to a place you love, which is why I’ve done it slowly,” Mr. Horn said in a statement. “But with Alan Bergman leading the way, I’m confident the incredible Studios team will keep putting magic out there for years to come.” Mr. Bergman, a steady hand at Disney’s movie division since 1996, succeeded Mr. Horn as chairman of Disney Studios Content last year.

Mr. Bergman, 55, called Mr. Horn “one of the most important mentors I’ve ever had.”

Mr. Horn’s retirement adds to brain drain at the world’s largest entertainment company as a new generation of executives rise to power — led by Bob Chapek, who became chief executive last year. While not unexpected, the parade of retirements has contributed to an unsettled feeling inside the conglomerate, which is still recovering from an almost complete shutdown during the early part of the pandemic.

Robert A. Iger, the executive chairman, is decamping in December. Alan N. Braverman, Disney’s top lawyer, and Zenia B. Mucha, its chief communications officer, plan to leave around the same time. Other departures have included Jayne Parker, who led human resources; Steve Gilula and Nancy Utley, who ran Searchlight, Disney’s art film studio; and Gary Marsh, a longtime Disney-branded television executive.

Mr. Horn’s entertainment career has spanned nearly 50 years. He joined Disney in 2012 after being squeezed out of a senior role at Warner Bros. to make room for a new generation of managers. At Warner, where he expertly steered the Harry Potter and Batman franchises, he forged a strategy that ultimately swept through Hollywood — focusing on effects-filled franchise pictures, or “tent poles,” that resonate overseas.

The growth at Disney’s movie division under his tenure was jaw-dropping. In 2012, Disney-distributed movies collected about $3.3 billion at the global box office. In 2019, the studio generated $9 billion in ticket sales.