This Is 40 is a 2012 American romantic comedy-drama film written and directed by Judd Apatow and starring Paul Rudd and Leslie Mann. A "sort-of sequel" to Apatow's 2007 film Knocked Up, the plot centers on married couple Pete (Rudd) and Debbie (Mann), whose stressful relationship is compounded by each turning 40. John Lithgow, Megan Fox, and Albert Brooks appear in supporting roles.

Filming was conducted in mid-2011, and This Is 40 was released in the United States on December 21, 2012. It received mixed reviews from critics, who praised its cast, acting (particularly Mann, Rudd and Fox) and the film's comedic moments and perceptive scenes, but criticized its overlong running time and occasional aimlessness. In March 2022, Apatow announced to be in early development of a third film, set 10 years later and titled This Is 50. As of September 2024, no further developments have been announced.