Ub Iwerks (Ubbe Ert Iwwerks) (March 24, 1901–July 7, 1971), was a two-times Academy Award winner American animator, cartoonist and special effects technician, who was famous for his work for Walt Disney. He was born in Kansas City, Missouri. His name is explained by his East Frisian roots — his father, Eert Ubbe Iwwerks, emigrated to the USA in 1869 from the village Uttum in East Frisia (northwest Germany).

Iwerks was responsible for the distinctive style of the earliest Disney animated cartoons. The first few Mickey Mouse cartoons were animated almost entirely by Iwerks. He was considered by many to be Walt Disney’s oldest friend, and spent most of his career with Disney. Iwerks and Disney had a falling-out, and their friendship was severed when Iwerks accepted a contract with a competitor to leave Disney and start an animation studio under his own name.

The Iwerks Studio opened in 1930. Financial backers led by Pat Powers suspected that Iwerks was responsible for much of Disney’s early success. However, while animation for a time suffered at Disney from Iwerks’ departure, it soon rebounded as Disney brought in talented new young animators. The Iwerks Studio enjoyed no great success and failed to rival the top Disney and Fleischer Studios. The backers withdrew further financial support from Iwerks Studio in 1936, and it soon folded. After this, Ub Iwerks worked for a time for Columbia Pictures, before returning to work for Disney in 1940.

After his return to Disney Studios, Iwerks mainly worked on developing special visual effects, like his Academy Award nominated achievement for Alfred Hitchcock’s The Birds. He is credited as developing the processes for combining live action and animation used in Song of the South. He also worked at WED Enterprises, now Walt Disney Imagineering, helping to develop many Disney theme park attractions during the 1960s.

Iwerks’s most famous work outside animating Mickey Mouse was Flip the Frog for his own studio. Flip bears more than a small resemblance to the characters Iwerks drew earlier, Mickey Mouse and Oswald the Lucky Rabbit.

Iwerks was known for his fast work at drawing and animation and his wacky sense of humor. Animator Chuck Jones, who worked for Iwerks’ studio in his youth, said “Iwerks is Screwy spelled backwards.” Ub Iwerks died in 1971 of a heart attack in Burbank, California, aged 70.

A documentary film, The Hand Behind the Mouse: The Ub Iwerks Story was released in 1999, followed by a book written by Leslie Iwerks and John Kenworthy in 2001.