With the rapid development in the exploration of marine resources, coastal geohazard and offshore geotechnics have attracted a great deal of attention from coastal geotechnical engineers and has achieved significant progress in recent years. With the complicated marine environment, numerous natural marine geohazard have been reported in the world, e.g., South China Sea. In addition, damage of offshore infrastructures (monopile, bridge piers, etc.) and supporting installations (pipelines, power transmission cables, etc.) have occurred in the last decades. A better understanding of the fundamental mechanism and soil behavior of the seabed in the marine environments will help engineers in the design or planning of the coastal geotechnical engineering projects. The purpose of this Special Issue is to present with the recent advances in the field of coastal geohazard and offshore geotechnics. This Special Issue will provide researchers updated development in the field and possible further developments. In this Special Issue, eighteen papers were published, covering three main themes: (1) mechanism of fluid–seabed interactions and its associate seabed instability under dynamic loading [1–5]; (2) evaluation of stability of marine infrastructures, including pipelines [6–8], piled foundation and bridge piers [9–12], submarine tunnel [13], and other supported foundations [14]; and (3) coastal geohazard, including submarine landslide and slope stability [15,16] and other geohazard issue [17,18]. More details of each contribution are summarized in the following subsections.