Idealness of k-wise intersecting families -- Flexible Graph Connectivity: Approximating Network Design Problems Between 1- and 2-connectivity -- Faster Algorithms for Parametric Global Minimum Cut Problems -- Optimizing Sparsity over Lattices and Semigroups -- A Technique for Obtaining True Approximations for k-Center with Covering Constraints -- Tight Approximation Bounds for Maximum Multi-Coverage -- Implementing automatic Benders decomposition in a modern MIP solver -- Improved Approximation Algorithms for Inventory Problems -- Extended Formulations for Stable Set Polytopes of Graphs Without Two Disjoint Odd Cycles -- On a generalization of the Chv atal-Gomory closure -- Algorithms for ows over time with scheduling costs -- Integer Plane Multi ow Maximisation: Flow-Cut Gap and One-Quarter-Approximation -- Stochastic Makespan Minimization in Structured Set Systems -- Continuous facility location on graphs -- Recognizing even-cycle and even-cut matroids -- A combinatorial algorithm for computing therank of a generic partitioned matrix with $2 ntimes 2$ submatrices -- Fair Colorful k-Center Clustering -- Popular Branchings and Their Dual Certi cates -- Sparse graphs and an augmentation problem -- About the Complexity of Two-Stage Stochastic Ips -- Packing under Convex Quadratic Constraints -- Weighted Triangle-free 2-matching Problem with Edge-disjoint Forbidden Triangles -- Single source unsplittable ows with arc-wise lower and upper bounds -- Maximal quadratic-free sets -- On Generalized Surrogate Duality in Mixed-Integer Nonlinear Programming -- Andrea Lodi and Felipe Serrano -- The integrality number of an integer program -- Persistency of Linear Programming Relaxations for the Stable Set Problem -- Constructing lattice-free gradient polyhedra in dimension two -- Sequence independent lifting for the set of submodular maximization problem -- A Fast (2 + 2/7)-Approximation Algorithm for Capacitated Cycle Covering -- Graph Coloring Lower Bounds from Decision Diagrams -- On convex hulls of epigraphs of QCQPs -- On the convexi cation of constrained quadratic optimization problems with indicator variables.

This book constitutes the refereed proceedings of the 21st International Conference on Integer Programming and Combinatorial Optimization, IPCO 2020, held in London, UK, in June 2020. The 33 full versions of extended abstracts presented were carefully reviewed and selected from 126 submissions. The conference is a forum for researchers and practitioners working on various aspects of integer programming and combinatorial optimization. The aim is to present recent developments in theory, computation, and applications in these areas.