Fi is a first internet TV series in Turkey, the Turkish psychological thriller television series originally streamed online by puhutv. It is an adaptation of award-winning author Azra Kohen's trilogy novels Fi, Çi, and Pi. Its first season consists of 12 episodes which were released from 31 March 2017 to 16 June 2017. The second season started in October 2017.

Within 50 hours of the first three episodes being released, it reached 3.5 million viewers. The first 9 episodes reached 50 million viewers. According to statistics that were collected by various Turkish agencies, among the 48 million Internet s in Turkey, the number of s watching Fi at the time was 8 million.

The second season of the series have a different story than the books. This became a big problem for the readers and followers of Azra Kohen. The author canceled the series due to fact that the production company did not adhere to the original plot and depth of content of the trilogy and sue the production company Ay Yapim. The case is still in court (2022).