Swiftest is a software package designed to model the long-term dynamics of system of bodies in orbit around a dominant central body, such a planetary system around a star, or a satellite system around a planet. The main body of the program is written in Modern Fortran, taking advantage of the object-oriented capabilities included with Fortran 2003 and the parallel capabilities included with Fortran 2008 and Fortran 2018. Swiftest also includes a Python package that allows the user to quickly generate input, run simulations, and process output from the simulations. Swiftest uses a NetCDF output file format which makes data analysis with the Swiftest Python package a streamlined and flexible process for the user. Building off a strong legacy, including its predecessors Swifter and Swift, Swiftest takes the next step in modeling the dynamics of planetary systems by improving the performance and ease of use of software, and by introducing a new collisional fragmentation model. Currently, Swiftest includes the four main symplectic integrators included in its predecessors: WHM, RMVS, HELIO, and SyMBA. In addition, Swiftest also contains the Fraggle model for generating products of collisional fragmentation.