Ship detection and segmentation in optical remote sensing (ORS) images is a current concern actively addressed by the academic community owing to its vast applications. Most present methods only detect the location of the ship but do not segment it at the pixel level. Considering the complex background of ORS images, identifying ships from interferences, such as clouds, waves, and some land architectures similar to ships, proves to be difficult. To address this issue, we propose a high-resolution representation and multistage region-based network (HR-MSRN) for ship detection and segmentation from ORS images. HR-MSRN mainly consists of three parts: the high-resolution feature pyramid network (HRFPN), region proposal network (RPN), and multistage detection and segmentation network (MSDSN). First, HRFPN is built as a backbone network to extract and fuse multilevel image feature maps. Second, ship candidate boxes are generated by defining numerous anchors through RPN. Third, using the idea of a cascade mask R-CNN as the reference method, the MSDSN is proposed to obtain the ship localization and mask shape. We utilize the proposed framework to evaluate an Airbus-ship dataset, and the experiments indicate that (1) HRFPN provides better feature representation ability than the ResNet-FPN when maintaining the same detection framework, especially for small ships; (2) the direct flow between mask branches refines the mask information, and the semantic segmentation branch enhances context information, which indicates that MSDSN is effective and promotes further improvements in ship detection and segmentation from ORS images; (3) in comparison to other region-based methods, HR-MSRN obtains superior performance of ship detection and segmentation in the ORS imagery.