We review the basic ideas behind numerical simulations of quantum field theory, which lead to non‐perturbative results in particle physics. We first sketch the functional integral formulation of quantum mechanics, its transition to Euclidean time and the link to statistical mechanics. Then we proceed to quantum field theory in the lattice regularization, and its applications to scalar fields, gauge fields and fermions. In particular we address the treatment of chiral symmetry. At last we describe the formulation of lattice QCD and comment on simulations and results.