The master's thesis is divided into two parts, a theoretical and a practical part. In the theoretical part of the thesis, the most commonly used process improvement and process management methodologies - Lean and Six Sigma - with the description of their history and real industry examples, are defined and explained in detail. In addition to the basic principles of each methodology, the most commonly used tools are listed and explained, along with their function and impact of their application on process improvement in the automotive industry and industry in general. The benefits of combining beforementioned methodologies for their complementary qualities - which results in increased productivity and quality, reduced costs and a safer environment for employees and customers – are mentioned as well. In the practical part of the thesis, which took place in the company Bugatti Rimac d.o.o., the Lean Six Sigma strategy with its associated tools was applied to the production process of an electric car. In addition to the review of the current performance of the process, an analysis of the potential causes of the problem was also carried out. After implementing proposed solutions, a system was developed to monitor the indicators of the implementation success. Appropriate measures to maintain the process in an improved state were designed as well.