Research Infrastructures (RIs) constitute a diverse set of organisations, yet they exhibit common characteristics: they operate as complex, stakeholder-intensive environments within a rapidly evolving scientific landscape and are staffed by highly qualified personnel who both support and conduct research. These features underscore the critical role of effective leadership. However, traditional managerial models, grounded in stable structures and detailed planning, are often insufficient in scientific contexts. This chapter examines how leadership is conceived and practised in two diverse European RIs—CERN, a large single-site facility, and ELIXIR, a distributed infrastructure—to illustrate how leadership development serves as a strategic lever for organisational effectiveness. Through examining their respective approaches, the chapter identifies shared challenges as well as distinct responses, providing broader insights into leadership within RIs undergoing continual scientific and organisational change.