Ground-based high frequency (3–30 MHz) surface wave radar (HFSWR) and microwave (S-band: ~3 GHz or X-band: ~10 GHz) marine radar have been widely used in ocean remote sensing for over four decades. HFSWR systems are able to monitor sea surface currents, winds, waves, and targets “over the horizon” (up to 300 km) due to the strong interaction between HF radio signals and ocean gravity waves. Compact microwave marine radar covers the line-of-sight area with a relative high spatial resolution finer than 10 m and can be deployed on ships. This enables S-band or X-band radar to be an ideal sensor for marine navigation or provide finer sea surface currents, waves, and winds measurement for the area of interest.

Due to increasing development of HF radar networks worldwide and new applications of regular microwave marine radars for expanding coastal ocean observing capabilities and improving human marine activity safety, the purpose of this special issue is to present the state-of-the-art developments and success or challenge in ocean remote sensing applications by leading researchers and practitioners of both HF and microwave radars.

Potential topics include, but are not limited to:

• Novel antenna design for HF and microwave marine radar systems
• Recent development of HF radar cross sections
• Advances in modelling marine radar scattering from ocean surface
• Adaptive and nonlinear methods for signal processing in HF and microwave marine radars
• New applications of HF and microwave marine radars