Borlänge ([ˈbôːˌɭɛŋːɛ]) is a locality in Dalarna County, Sweden, with 44,898 inhabitants as of 2020. It is the seat of the Borlänge Municipality which as of 2017 had a total population of 51,604 inhabitants.

Originally Borlänge was the name of a tiny village, and traces back to at least the 1390s. The village was insignificant up until about 1870. In 1872 the construction of Domnarfvets Jernverk, the ironworks of neighbouring village Domnarvet started. In 1875 a railway between Falun and Ludvika, via Borlänge was inaugurated. Thanks to its railway station the village of Borlänge became highly important in servicing the ironworks.

In 1898, Borlänge was granted privileges by the national Swedish government as a market town (Swedish: köping) with about 1,300 inhabitants, but still today it belongs to the Church of Sweden's regionally historically dominant parish of Stora Tuna, centered on a large medieval church by that name (meaning great enclosed farmyards), now located in a rural district east of the city. In 1898, the Stora Kopparbergs Bergslag - the owner of the ironworks in Domnarvet at the time - built a papermill in an adjacent village to Borlänge called Kvarnsveden, upstream from Domnarvet. Many area residents emigrated to the United States in the late 19th and early 20th centuries.

In 1944, the City of Borlänge was incorporated after the market town joined the industrial towns of Domnarvet and Kvarnsveden. In 1971 the municipality of Borlänge was established when the Stora Tuna municipality merged with the City of Borlänge.

From the 1940s onward, politics in the municipality has been dominated by the Social Democratic Party.

In the early 1970s, the Kvarnsvedens Pappersbruk paper mill and the Domnarvets Jernverk steel mill had a high demand for employees.

Between 1970 and 1974, the Tjärna Ängar Million Programme district was built.

In the 1990s, Borlänge had the highest crime rate per thousand inhabitants in Sweden, dominated by violence and theft.