RasMol is a computer program written for molecular graphics visualization intended and used mainly to depict and explore biological macromolecule structures, such as those found in the Protein Data Bank (PDB).

[1] Historically, it was an important tool for molecular biologists since the extremely optimized program allowed the software to run on (then) modestly powerful personal computers.

RasMol includes a scripting language, to perform many functions such as selecting certain protein chains, changing colors, etc.

These have been uploaded by researchers who have characterized the structure of molecules usually by X-ray crystallography, protein NMR spectroscopy, or cryogenic electron microscopy.

Rasmol can communicate with other programs via Tcl/Tk on Unix platforms, and via Dynamic Data Exchange (DDE) on Microsoft Windows.