In an attempt to fill that gap, we present Gromologist, a Pythonic utility library oriented at custom manipulation of Gromacs topologies. For many years now, Gromacs has been not only the most broadly used but also one of the fastest-growing MD engines in the field of molecular simulations and has a well-established user base, whichcombined with the ease of format interconversion allowed by other tools -makes Gromologist a broadly applicable tool for all types of non-standard operations including, but not limited to, adding and removing atoms and bonds, introducing amino acid mutations in both the structure and topology, checking and listing force field parameter compatibilities, looking for mismatches between structures and topologies, merging files, manipulating alchemical states, modifying force field types or combination rules, parameter optimization or automated editing of structures. In addition, we maintain a strict zero-dependency policy (except for a few very specific features), so that the library is conveniently lightweight and can be easily installed with any modern Python distributions without causing dependency conflicts.