Annotation plays a key role in the creation of reference datasets that are useful to evaluate medical image processing algorithms and to train machine learning based architectures. RVXLiverSegmentation is a 3D Slicer plug-in aiming at speeding-up the annotation of liver anatomy from medical images (CT -Computerized Tomography-scans or MRI -Magnetic Resonance Imaging- for instance). This organ has particular anatomy and physiology; within its parenchymal volume, the liver receives blood from the portal vein and hepatic artery (the former one being the most visible in medical images), and delivers filtered blood through the hepatic veins, toward inferior vena cava. The blood vessels subdivide into the liver as fine vascular tree structures, which make the segmentation difficult, mostly in MRI modality. To facilitate this task, our plug-in is decomposed into modules dedicated to the segmentation of the liver volume, inner vessels and possible tumors. RVXLiverSegmentation can be downloaded or installed from the 3D Slicer software as an official module.