Queueing Networks QNs are a useful performance modelling notation. They can be used to describe many kinds of systems, and efficient solution techniques have been developed for some classes of QN models. Despite the fact that QNs have been extensively studied, very few software packages for QN analysis are available today. In this paper we describe the qnetworks toolbox, a free software package for QN analysis for GNU Octave. qnetworks provides implementations of solution algorithms for single station queueing systems as well as for product and some non product form QN models. Exact, approximate and bound analysis can be performed. Additional utility functions and algorithms for Markov Chains analysis are also included. The qnetworks package is available as free and open source software, allowing users to study, modify and extend the code. This makes qnetworks a viable teaching tool.