Dr. Ian Donnelly is a fictional character from the 2016 science fiction film, Arrival. He is portrayed by actor Jeremy Renner and serves as a physicist who collaborates with linguist Louise Banks, played by Amy Adams, to communicate with extraterrestrial beings. In the film, Dr. Donnelly's expertise in physics complements Louise's linguistic skills as they work together to understand the complex language of the alien species known as the Heptapods. His character plays a crucial role in unraveling the mysteries surrounding the aliens' arrival on Earth and the implications of their communication.