The One and Only Ivan is a 2012 novel written by Katherine Applegate and illustrated by Patricia Castelao. It is about a silverback gorilla named Ivan who lived in a cage at a mall, and is written from Ivan's point of view. In 2013 it was named the winner of the Newbery Medal. It has won several other awards and is currently nominated to several reading lists. It was followed in 2020 by The One and Only Bob, presented from the point of view of Ivan's best friend, the dog Bob. A second sequel, The One and Only Ruby, was published in 2023.

Ivan was a western lowland gorilla born in 1962 in what is now the Democratic Republic of the Congo. He was captured from the wild as a baby and brought to live with humans. For the first few years of his life he lived with his owners, but he soon grew too big for a human house and they moved him to a 14' x 14' concrete enclosure on display to the public at the B&I shopping center in Tacoma, Washington, where he spent the next 27 years of his life.