20 Days in Mariupol (Ukrainian: 20 днів у Маріуполі, romanized: 20 dniv u Mariupoli) is a 2023 Ukrainian documentary film directed by Mstyslav Chernov. The film tells the story of the twenty days Chernov spent with his colleagues in besieged Mariupol after Russia began its invasion of Ukraine. Chernov compiled footage that he collected in Mariupol together with the team from Frontline and the Associated Press (AP).

The film premiered on 20 January at the 2023 Sundance Film Festival where it won the Sundance World Cinema Documentary Competition. It was selected as the Ukrainian submission for the Best International Feature Film at the 96th Academy Awards, and made the December shortlist, but was not nominated for International Feature Film, but received a Best Documentary Feature nomination. Film also was nominated for BAFTA in 2 categories, and won Directors Guild of America Awards. It received critical acclaim and was named one of the top 5 documentary films of 2023 by the National Board of Review. Film was screened at the start of the 78th session of the UN General Assembly. Film received more than 20 awards and 40 nominations in general.