The War with Grandpa is a 2020 American family comedy film directed by Tim Hill, from a screenplay by Tom J. Astle and Matt Ember, based upon the novel of the same name by Robert Kimmel Smith. The film is about a young boy named Peter (Oakes Fegley) who fights in a prank war with his grandfather (Robert De Niro) to get his grandfather to move out of his room after he moves in with his family. Uma Thurman, Rob Riggle, Laura Marano, Cheech Marin, Jane Seymour, and Christopher Walken also star.

Originally filmed in May 2017, The War with Grandpa's release was delayed several times due to photography changes and the closure of The Weinstein Company, the original distributor. The film was eventually released theatrically in the United States on October 9, 2020 by 101 and Brookdale Studios, as well as abroad beginning in August 2020 by Brookdale Studios. It received generally negative reviews from critics and grossed $43 million worldwide against a production budget of $38 million.