The spectral-cube package provides an easy way to read, manipulate, analyze, and write data cubes with two positional dimensions and one spectral dimension, optionally with Stokes parameters. It provides a uniform interface to spectral cubes, robust to the wide range of conventions of axis order, spatial projections, and spectral units that exist in the wild. It also allows easy extraction of cube sub-regions using physical coordinates and the ability to easily create, combine, and apply masks to datasets. It is designed to work with datasets too large to load into memory.