Fiber-reinforced composite (FRC) materials are widely used in advanced structures and are often applied in order to replace traditional materials such as metal components, especially those used in corrosive environments. They have become essential materials for maintaining and strengthening existing infrastructure due to the fact that they combine low weight and density with high strength, corrosion resistance, and high durability, providing many benefits in performance and durability. Modified fiber-based composites exhibit better mechanical properties, impact resistance, wear resistance, and fire resistance. Therefore, the FRC materials have reached a significant level of applications ranging from aerospace, aviation, and automotive systems to industrial, civil engineering, military, biomedical, marine facilities, and renewable energy. In order to update the field of design and development of composites with the use of organic or inorganic fibers, a Special Issue entitled "Progress of Fiber-Reinforced Composites: Design and Applications" has been introduced. This reprint gathers and reviews the collection of twelve article contributions, with authors from Europe, Asia and America accepted for publication in the aforementioned Special Issue of Applied Sciences.