Lahti (, ; ) is a city in Finland and the regional capital of Päijät-Häme. It is located in the Finnish Lakeland. The population of Lahti is approximately , while the sub-region has a population of approximately . It is the most populous municipality in Finland, and the sixth most populous urban area in the country.
Lahti is situated on a bay at the southern end of lake Vesijärvi about north-east of the capital city Helsinki, south-west of Heinola and east of Hämeenlinna, the capital of the region of Kanta-Häme. Lahti is situated at the intersection of Highway 4 (between Helsinki and Jyväskylä) and Highway 12 (between Tampere and Kouvola), which are the most significant main roads of Lahti. Its neighboring municipalities are Asikkala, Heinola, Hollola, Iitti and Orimattila.
Lahti is a long-time pioneering city in environmental sustainability, dating back to as early as 1990 and before. The European Commission has named Lahti as the European Green Capital of 2021. Lahti is also the headquarters of the Salpausselkä UNESCO Global Geopark, one of 4 UNESCO Geoparks in Finland; Salpausselkä was added to the list of over 170 UNESCO Global Geoparks in the world in 2022. In January 2026, the British newspaper The Guardian highlighted Lahti as one of its readers' favorite travel destinations in the Nordic countries, praising its good transport connections from Helsinki, charming little cafes and "quiet, down-to-earth people". <!-- Some inacceptably-minded person had glued the preceding sentence to the one about criminality to make it be easily overlooked. -->
The coat of arms of the city depicts a train wheel surrounded by flames. It refers to the Riihimäki–Saint Petersburg railway, which had a decisive influence on the birth of the city at its crossroads.
Etymology
In English, the Finnish word Lahti literally means 'bay'. Lahti is also dubbed the "Chicago of Finland" due to the similarity of early industries of both cities, when they were known as "slaughterhouse cities". Also, the troubled history of both cities in terms of crime has been seen as one of the similarities.
In December 2018, Lahti became the first new university city in Finland after Rovaniemi in 1979 when the Parliament accepted a change in the university law. LUT University nowadays consists of two campuses, Lappeenranta and Lahti.
Geography
thumb|right|[[Vesijärvi|Lake Vesijärvi seen from Lahti]]
The terrain of Lahti is dominated by the first Salpausselkä ridge, a terminal moraine that cuts through the city from west to east. The city is located in the transition from the southern coastal area to the Finnish Lakeland; prominent to the north of the Salpausselkä are rocky hills and fragmented lakes, while its south side is dominated by forests and small rivers. The divide is also apparent in the soil, which mostly consists of till in the north and clay in the south. The biggest lake is Vesijärvi which also is a gateway to Central Finland via Lake Päijänne. There is also a pond called Pikku-Vesijärvi ("Little Vesijärvi") near the Lanu-puisto park.
Subdivisions
The area of the city of Lahti is divided in two ways: first, the 40 individually numbered districts (), and second, the 9 greater areas (), which are divided into 41 statistical districts () and further into 169 statistical areas (). The definitions of the districts and statistical districts do not necessarily match each other. Below are listed the districts:
- Keski-Lahti
- Kartano
- Paavola
- Niemi
- Kiveriö
- Kivimaa
- Mukkula
- Kilpiäinen
- Pesäkallio
- Kytölä
- Viuha
- Kunnas
- Ahtiala
- Koiskala
- Myllypohja
- Möysä
- Järvenpää
- Kolava
- Kujala
- Kerinkallio
- Ämmälä
- Renkomäki
- Nikkilä
- Laune
- Asemantausta
- Sopenkorpi
- Hennala
- Jokimaa
- Okeroinen
- Kärpänen
- Pirttiharju
- Salpausselkä
- Jalkaranta
- Villähde
- Nastola
- Uusikylä
- Seesta
- Ruuhijärvi
- Immilä
- Pyhäntaka
Climate
Under the Köppen climate classification, Lahti has a humid continental climate (Dfb). Summers are usually warm in the city, with the average daily temperature in July exceeding over 23 °C (73.6 °F) and also having had the most 25 °C (77 °F) (or more) days in the last two decades, alongside Kouvola. Winters are cold and long but as a result of the climate change, specially winters are becoming more and more mild. During the heatwave of 2010, the temperature in Lahti reached 35.0 °C (95 °F). The amount of precipitation is fairly evenly distributed throughout the year. The driest season is spring, the most precipitation is in the second half of the year.
Demographics
Population
The city of Lahti has inhabitants, making it the most populous municipality in Finland. The Lahti region has inhabitants, making it the fifth largest region in Finland after Helsinki, Tampere, Turku and Oulu. Lahti is home to 2% of Finland's population. 11% of the population has a foreign background, which is close to the national average. However, it is lower than in the major Finnish cities of Helsinki, Espoo, Tampere, Vantaa or Turku.