Diary is a 2022 Indian Tamil-language supernatural mystery thriller film written and directed by debutant Innasi Pandiyan and produced by S. Kathiresan. The film was distributed by his cousin Udhayanidhi Stalin under his banner Red Giant Movies. The film features Arulnithi and Pavithra Marimuthu in lead roles. The film's music and score is composed by Ron Ethan Yohann, with cinematography handled by Aravinnd Singh and editing done by S. P. Raja Sethupathi. It was shot extensively across Tamil Nadu including Chennai, Coonoor, Ooty, Mettupalayam and Coimbatore.

The film was initially scheduled to be released in theatres on 11 August 2022, but got postponed and released on 26 August 2022, due to the clash with Dhanush's Thiruchitrambalam. Diary received highly positive reviews from critics and audience, and completed 50 days of it theatrical run and was declared a blockbuster at the box office.