O2 (also known as Dawn of War in the UK) is a 2020 Estonian-Latvian-Lithuanian-Finnish historical spy thriller film, directed by Margus Paju, starring Sampo Sarkala, Kaspars Znotiņš, Elmo Nüganen, Rein Oja and Tambet Tuisk. The film is about the Estonian intelligence officer Feliks Kangur (played Priit Võigemast) tried to find out a traitor in the secret service in 1939, on the eve of Estonia losing its independence. The film was written by Tom Abrams, Tiit Aleksejev, Eriikka Etholén-Paju and Olle Mirme.

The film was produced by Nafta Films (Estonia) and Taska Film (Estonia), and coproduced by Film Angels Studio (Latvia), IN SCRIPT (Lithuania) and Finland's Solar Films. It was supported by the Estonian Film Institute. The film was released in cinemas in Estonia on 9 October 2020.