<p>Ultrafast phenomena induced by femtosecond laser irradiation encompass a range of highly dynamic physical processes, including but not limited to electron excitation, material ablation, plasma generation, and shock wave propagation. Unveiling the dynamics of these ultrafast processes is crucial for effectively controlling laser processing. However, many of these phenomena occur on timescales ranging from femtoseconds (fs) to nanoseconds (ns), which presents significant challenges in monitoring and interpretation; thus, ultrafast optical imaging techniques are often required. This paper comprehensively reviews the ultrafast optical imaging methods employed in recent years to monitor various ultrafast processes such as electron excitation, ultrafast ablation, plasma ejection, and shock wave propagation during femtosecond laser processing of metallic, composite, and ceramic materials. These methods can be categorized into two primary types: pump-probe ultrafast optical imaging and single-shot ultrafast optical imaging techniques. The working principles and key findings associated with each type of ultrafast optical imaging technique are described in detail. Finally, the imaging principles, advantages and disadvantages, and application scenarios of various ultrafast imaging technologies are summarized, along with a discussion of future challenges and development directions in this field.</p> Graphical abstract <p></p>