Many organizations are planning to engage in the monetization of data. However, it turns out to be a practical problem where to start and what to build on from the existing capabilities. A maturity model helps assess the maturity of the actual capabilities. At the same time the same model can be used to prescribe a desired target state. The gap between the target state and the actual status helps setting up actions to remedy the situation. This paper proposes a Data Maturity Model (DMMM), the first maturity model for data monetization. It has been scientifically developed bottom up based on literature and extensive expert knowledge and its first release is extensively documented here.