CNH Industrial Österreich GmbH is a tractor production plant in Lower Austria. Currently there are the management systems ISO 9001:2008, ISO 14001:2004, OHSAS 18001: 2007 and ISO 50001:2011 and a lean manufacturing system called World Class Manufacturing (WCM) implemented. There have been some minor integration activities in the past but there has not been a structured approach behind it. The target of this master thesis is to integrate the normed management systems and to create an integrated management system. In a further step, specific tools from lean management should be linked to the system. To realize the task a literature research needs to be done to define terms like management or management system. Also, the functionalities of the systems ISO 9001:2008, ISO 14001:2004, OHSAS 18001: 2007 and ISO 50001:2011 need to be clarified and an overview about lean management needs to be stated. As a last topic of the literature research there will be a summary about methods for integrating management systems presented. As a next step, there will be an overview given about the current situation of the implemented normed standards and the lean management system WCM in St. Valentin. In the main part of this master thesis the integration will be done. For this the cross-functional aspects of the four normed management systems need to be determined. On that base, the integrative need will be stated, the current status of integration will be described and the integration task per aspect will be developed. In a next step, specific tools from lean management will be linked to the system and further described. In the last part of this thesis the integrated management system will be described. For this, a schematic model will be developed. After that, the process structure of the system will be described in detail. The last chapter is summarizing the results and is giving an outlook to the upcoming transition to the 2015 standards of the ISO norms, which have to be realized latest in 2018.