Peter Sís (born Petr Sís on May 11, 1949) is a Czech-born American illustrator, author, and filmmaker. He was born in Brno, Czechoslovakia, and grew up in Prague. His father was a filmmaker and his mother was an artist. He studied at the Academy of Applied Arts in Prague, graduating in 1974, and went on to study at the Royal College of Art in London, where he worked with illustrator Quentin Blake.

He began his career as a filmmaker and won the Golden Bear Award for an animated short at the 1980 Berlin Film Festival. In 1982, he traveled to the United States to create an animated film connected to Czechoslovakia's participation in the 1984 Los Angeles Olympics, during which he sought asylum and defected. He subsequently settled in New York, where the author and illustrator Maurice Sendak introduced him to the world of children's books. He also created the poster for the 1984 film Amadeus.

As an illustrator and author, he has received numerous major honors. Three of his books — Starry Messenger: Galileo Galilei (1996), Tibet Through the Red Box (1998), and The Wall: Growing Up Behind the Iron Curtain (2007) — were named Caldecott Honor Books by the American Library Association. The Wall also received the ALA's Robert F. Sibert Medal. In 2003, he became the first children's book illustrator to receive a MacArthur Fellowship. In 2012, he received the Hans Christian Andersen Award, widely considered the highest international honor in children's literature. His animated work is held in the permanent collection of the Museum of Modern Art in New York. He lives in the New York City area.