nctoolbox is a Matlab toolbox that provides read-only access to common data model datasets. Under the hood, nctoolbox uses NetCDF-Java as the data access layer. This allows nctoolbox to access NetCDF, OPeNDAP and HDF5 datasets using the same API. It has been tested with Matlab versions 2008a, 2008b, 2009a, and 2009b.