FC Lahti is a Finnish professional football club based in the city of Lahti. It currently plays in the Finnish second tier Ykkösliiga, after relegating from Veikkausliiga after the 2024 season. The homeground of Lahti is Lahden Stadion. Lahti is famous of being the local team of the most successful Finnish player, Jari Litmanen, who played for the club in two stints in 2004 and 2009–10. In his youth years and the start of his career, he played in Reipas Lahti.
Lahti was founded in 1996 when two rival clubs from Lahti – Kuusysi and Reipas Lahti (founded in Viipuri and moved to Lahti after Viipuri was ceded to USSR in 1947) – decided to merge. Also, the reserve club Pallo-Lahti was formed, but it was closed down after a couple of seasons due to economic difficulties. Both Reipas and Kuusysi controlled the junior section of the club.
Lahti played its first season in 1997, in the southern group of Ykkönen, the second tier of Finnish football. It finished second in the first half of the split league format Ykkönen, but was placed third in the final half, behind Haka and PK-35, both of which were promoted to Veikkausliiga. The next season, in 1998, saw success and Lahti finally gained promotion to the highest tier. They were relegated at the end of the 2010 season, but bounced back after just one season in Ykkönen.
In the premier division, Lahti has not yet achieved the success of Kuusysi and Reipas. In 2007, Lahti won the Finnish League Cup. In 2008 Lahti was third in the Veikkausliiga final table and was placed in the UEFA Europa League qualification rounds for season 2009. Lahti repeated the success in 2014 by finishing third for the second time in their history. The club qualified to the Europa League qualifiers for the third time in 2018 when the club finished fourth in the table the season before.
Lahti's reserve team played its last season in Kakkonen in 2017. After they were relegated to Kolmonen for the 2018 season, the team's activity was taken over by its administrational parent club Kuusysi.