Juho Väinö Valtteri Lähteenmäki (born 15 June 2006) is a Finnish football player for U19 team of Danish Superliga club Nordsjælland. Lähteenmäki started to play football in Ylöjärven Ilves in Ylöjärvi, before moving to Tampere and joining the Ilves youth academy. In January 2022, Lähteenmäki signed a deal with Danish club Nordsjælland, starting in July. On 11 December 2024, Lähteenmäki signed a new professional contract with Nordsjælland, valid until June 2028. On 23 February 2025, Lähteenmäki made his professional debut with the Nordsjælland first team in Danish Superliga, as a starting left back in a 3–2 home win against Sønderjyske. Lähteenmäki is a regular Finnish youth international, having represented Finland at under-16, under-17, under-18 and under-19 youth national team levels. In 2023, Lähteenmäki was part of the Finland U19 squad in the 2024 UEFA European Under-19 Championship qualification tournament, in three games against Romania, Czech Republic and San Marino.