Lauri Allan Törni was born in Viipuri, Viipuri Province, Karelia, Finland. His father was a ship captain named Jalmari (Ilmari) Törni. His mother was Rosa (née Kosonen) Törni. He had two sisters: Salme Lesley (b. 1920) and Kaija Iris (b. 1922). When he was a boy, he was athletic. An early friend was future Olympic Boxing Gold Medalist Sten Suvio. He attended business school and served with the Finland Civil Guard. Then he entered military service and joined the 4th Independent Jaeger Infantry Battalion stationed at Kiviniemi.