The Happiest Day in the Life of Olli Mäki (Finnish: Hymyilevä mies, lit. 'Smiling man') is a 2016 biographical drama film directed by Juho Kuosmanen and written by Mikko Myllylahti and Kuosmanen. An international co-production between Finland, Sweden, and Germany, the film stars Jarkko Lahti, Oona Airola, and Eero Milonoff. It tells the true story of Olli Mäki, the famous Finnish boxer who had a shot at the 1962 World Featherweight title.

The film had its world premiere at the 69th Cannes Film Festival on 19 May 2016, where it was awarded the Un Certain Regard prize. It was theatrically released in Finland on 2 September 2016, by B-Plan Distribution. It received generally positive reviews from critics and was selected as the Finnish entry for the Best Foreign Language Film at the 89th Academy Awards, but it was not nominated. At the 71st Jussi Awards, the film earned a leading ten nominations and won in eight categories, including Best Film, Best Director, Best Actor (for Lahti), and Best Supporting Actress (for Airola). Kuosmanen also won the European Discovery at the 29th European Film Awards.