Suomenlinnan Liikenne Oy (SLL) is a subsidiary company of the Helsinki City Transport (HKL). It operates the public transport between the city and the Suomenlinna fortress as part of the public transport system organised by the Helsinki Region Transport (HSL).

Suomenlinnan Liikenne Oy is owned by the City of Helsinki.

Suomenlinnan Liikenne Oy’s office is located at the head quarters of HKL at address Hämeentie 86 A 2. floor 00550 Helsinki. No tickets are sold at the premises.