TurtleSeg is an interactive tool that generates a 3D segmentation from a small number of contoured slices generated with minimal user guidance. The program is based on the LiveWire algorithm which automatically produce a dense set of parallel segmentation contours from a sparse set of user provided contours. The program incorporates an automated system for automatically directing the user towards the next best place for them to provide input. 3D navigation with oblique slice planes is provided, and the program can read and write a range of 3D file formats. There is extensive documentation in the form of a manual, FAQ, and video tutorials