Sparselizard (GNU GPLv2+, Copyright (C) 2020-2021 A. Halbach, Copyright (C) 2018-2019 A. Halbach, IMEC, Copyright (C) 2017 A. Halbach and C. Geuzaine, University of Liege) is a high-performance, multiphysics, hp-adaptive, open source C++ finite element library running on Linux, Mac and Windows. It is carefully validated against analytical solutions, third party software and lab measurements. General high-performance domain decomposition methods are available for large-scale simulations on computing clusters (contact Quanscient for commercial applications). Efficient conformal adaptive mesh refinement (AMR) is provided for 3D, 2D and 1D problems. A fast algorithm for mesh-to-mesh interpolation and a general implementation of the mortar finite element method allow to easily work with non-matching meshes and provide general periodic conditions. FEM simulations can be weakly or strongly coupled to lumped electric circuits. Sparselizard can handle a general set of problems in 3D, 2D axisymmetric, 2D and 1D such as mechanical (anisotropic elasticity, geometric nonlinearity, buckling, contact, crystal orientation), fluid flow (laminar, creeping, incompressible, compressible), stabilized advection-diffusion, nonlinear acoustic, thermal, thermoacoustic, fluid-structure interaction, electric, magnetic, electromagnetic, piezoelectric, superconductor,... problems with a transient, (multi)harmonic or damped/undamped eigenmode analysis. A massive amount of data can be stored for delayed, remote post-processing thanks to the ultra compact .slz data format. Problems with several millions of unknowns in 3D and several tens of millions of unknowns in 2D have been solved within minutes on up to 32 cores/64 threads (see report). Some built-in geometry definition and meshing tools are also provided.