This chapter explores the nature and characteristics of co-offending and co-offending groups in Norway, using the rich – and relatively unexplored – information about ­co-offending that is found in Norwegian official registers. It focuses on data from Norwegian administrative registers as kept and provided by Statistics Norway. The chapter draws on information from the population registry to explore variations in co-offending depending on the offender’s sex, age at offence and immigrant background. It discusses the nature and characteristics of ­co-offending and co-offending groups in Norway. Crime type is one of the most widely explored correlates of co-offending, and co-offending is typically found to be more common in, e.g., burglaries, robberies and vehicle thefts than in, e.g., drug possessions or violent and sexual offences. Co-offending is defined as the commission of an offence by more than one person, and one of the most well-established findings in the study of co-offending is that it is relatively common.