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 had its world premiere at the 2023 Sundance Film Festival, where it won the Sundance World Cinema Documentary Competition. It was selected as the Ukrainian submission for the Academy Award for Best International Feature Film at the 96th Academy Awards, but it was instead nominated in the Best Documentary Feature Film category and went on to win the award. The film was also nominated for two BAFTAs and won one of them, also won a Directors Guild of America Award and Ukrainian National Film Academy Award.

The film has received critical acclaim and was named one of the top five documentary films of 2023 by the National Board of Review. The film was also screened at the start of the 78th session of the UN General Assembly.