The Meschach Library is a numerical library of C routines for performing calculations on matrices and vectors. It is intended for solving systems of linear equations (dense and sparse), solve least squares problems, computing eigenvalues and eigenvectors, etc. We do not claim that it contains every useful algorithm in numerical linear algebra, but it does provide a basis on which more advanced algorithms can be built. The library is for people who know something about the C programming language, something of how to solve the numerical problem they are faced with but do not want to have the hassle of building all the necessary routines from the scratch. The library is not a loose collection of numerical routines but it comprises a coherent system. The current version is enhanced with many features comparing with previous versions. Since the memory requirements are nontrivial for large problems we have paid more attention to allocation/deallocation of memory. The source code is available to be perused, used and passed on without cost, while ensuring that the quality of the software is not compromised. The software is copyrighted; however, the copyright agreement follows in the footsteps of the Free Software Foundation in preventing abuse that occurs with totally public domain software.