The current container terminal market is facing challenging and uncertain times. The growth in container vessel size and high competition are pushing terminals to increase their storage capacity and productivity. In addition, environmental regulations and local governments are pushing terminals to reduce their environmental impact during terminal operations. Consequently, it is impossible for terminals to increase their productivity and terminal capacity without considering the environmental impact of container handling operations. This is the first paper of a two-part study that researches the readiness of certain clusters of container terminals to innovate their container handling operations. This paper identifies the variables that are essential for classifying European container terminals. By conducting a literature review, nine characteristics have been identified: equipment, level of terminal automation, spatial dimensions (yard layout, terminal size, terminal capacity, quay length), geographical location, port and terminal governance structure, throughput, available energy sources, and labor and union organization. The terminal clusters that come out of the classification, depend on the research goal. For this reason, the actual clustering of terminals will be performed in the second part of this research, as the actual clustering of terminals depends on the goal of that research as some clusters are better suited for certain research goals. In the second paper of this research, terminals will be clustered according to their readiness to implement specific container terminal innovations.