The Mechanical Systems Unit, with its 48 faculty members and more than 100 PhD students and postdocs, is the largest one in the Department of Mechanical Engineering. Its research activity is focused on the theoretical and experimental study of the dynamics of complex mechanical systems. The nine research lines of the Mechanical Systems Unit cover a number of areas, ranging from railway engineering to mechatronics, from automotive to wind engineering, and from mobility to the diagnostics of machines and transport infrastructures. Combining mathematical modelling and numerical simulation with in-lab and on-site testing, also taking advantage of the opportunities offered by digital technologies and modern data science algorithms, is how researchers here face research challenges. We promote an interdisciplinary approach to research, also based on the collaboration with other groups inside and outside the Department and with international strategic partners. The research unit has always had a strong commitment to the collaboration with the industrial world too. The strength of our group relies on our people, with their passion and their skills, and on our laboratories, unique at national and international level.