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. From 1996, their were only one original staff member left at start on 2026 season, Pekka Penttinen. 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. ==Honours==