Koi... Mil Gaya (Hindi pronunciation: [ˈkoːɪ mɪl ɡəjaː] transl. Someone...is found) is a 2003 Indian Hindi-language science fiction film directed and produced by Rakesh Roshan. It stars Hrithik Roshan, Preity Zinta and Rekha. In addition to writing the story, Rakesh Roshan also wrote the screenplay with Sachin Bhowmick, Honey Irani, and Robin Bhatt. Koi... Mil Gaya focuses on Rohit (Hrithik Roshan), a developmentally disabled man who contacts an extraterrestrial being (Indravardhan Purohit) with his late father Sanjay's (Rakesh Roshan) computer. The film follows his relationship with Nisha (Zinta), Rohit's friend, who falls in love with him.

After the release of the commercially and critically successful romantic film Kaho Naa... Pyaar Hai (2000), Roshan wanted to work again with his son Hrithik on a different type of film. In June 2001, during the 2nd IIFA Awards, he announced the second film when he received the Best Director award for Kaho Naa... Pyaar Hai. Principal photography was shot by Ravi K. Chandran and Sameer Arya from November 2001 to March 2003 on sets built by Sharmishta Roy in Canada, India, and New Zealand. Roshan's brother, Rajesh Roshan, composed the film's soundtrack and background score. American artists Mark Clobe and Craig Mumma spent ₹4 crore (US$500,000) on its visual effects.

Filmed on a budget of ₹25 crore (US$3.1 million) to ₹35 crore (US$4.4 million), Koi... Mil Gaya was released on 8 August 2003 and was the first instalment of the Krrish franchise. Promoted with the tagline "You Are Not Alone...", it targeted children and parents. It was the second-highest-earning Indian film of the year, grossing ₹82.326 crore (US$10 million) worldwide. The film had a positive critical reception, with most of the praise directed at the cast's performances. Two sequels titled Krrish and Krrish 3 were released in 2006 and 2013, respectively. A fourth installment, announced in 2016 and scheduled for release in December 2020, was postponed due to the COVID-19 pandemic.

The recipient of several awards, Koi... Mil Gaya won three National Film Awards (including Best Film on Other Social Issues). At the 49th Filmfare Awards, it was nominated in eleven categories and received five awards, including Best Film, Best Director (Rakesh Roshan), and Best Actor and Best Actor (Critics) (Hrithik Roshan). The film won five of its eleven nominations at the 5th IIFA Awards, including Best Director (Rakesh Roshan) and Best Actor (Hrithik Roshan). Considered a milestone of its genre, it is one of the first Indian films featuring aliens. The character of Jadoo became popular and inspired a spin-off series entitled J Bole Toh Jadoo (2004).