Earth observation missions have recently attracted a growing interest from the scientific and industrial communities, mainly due to the large number of possible applications capable to exploit remotely sensed data and images. Along with most remote sensing imagery now available in digital form, which can be easily copied and distributed through the Internet, the need of copyright protection arises as well. Such a problem has been largely addressed by resorting to image watermarking technology. We present a novel watermarking method based on a chaotic spread spectrum and apply it to the image products of remote sensing. The correlation property of chaotic sequences is analyzed. It is shown that the chaotic signal is more suitable to provide remote sensing image watermarks. In the retrieval process, the information signal is extracted by using a standard correlator. Experimental results show that the proposed chaotic watermarking system for remote sensing images is robust to various image manipulations, including resizing, cropping, filtering, and compression. Compared to the conventional spread spectrum watermarking approach, the proposed chaotic watermark is superior.