The Stockholm Metro (Swedish: Stockholms tunnelbana) is the metro system in Stockholm, Sweden. The system has 100 stations in use, of which 47 are underground and 53 above ground. There are seven lines numbered from 10 to 19, in three groups identified by a color: the Green, Red and Blue Lines. Each color line has two or three numbered lines on shared sections through the Stockholm City Centre.

Since the mid 1980s, the Stockholm Metro has been seriously affected by graffiti. Previously a train on which graffiti had been painted could remain in service for weeks and graffiti could remain in place at stations for months if not for years. Nowadays, however, trains with graffiti are taken out of service immediately and graffiti at stations is regularly cleaned up within a few days. The cost of graffiti and other types of vandalism has been calculated at approximately SEK 100 million per year.

During the 1990s, the Stockholm Transit System (SL) started outsourcing security to private security firms, some of which have been accused of using unlawful methods, such as the use of plain clothes guards and heavy-handed treatment of vandals arrested, and even heavy-handed treatment of ticketless passengers trying to escape. Since 2005, the Stockholm Police have assigned a special task force (Klotterkommissionen) to address the issues. The mainstay among the private security contractors in the fight against graffiti is the Commuter Security Group.